Audi Q5: Checking Pressures on Vehicles with Electrically Driven A/C Compressor
(Vehicles with Hybrid Drive)
General Information
Extremely Dangerous Due to High-Voltage
The high-voltage system is under high-voltage. Death or serious
bodily injury by electric shock.
- Individuals with electronic/medical life- and health sustaining
machines in or on their person cannot perform any work on high-voltage
systems. Life- and health sustaining machines are for example pain
killer pumps, implanted defibrillators, pacemakers, insulin pumps, and
hearing aids.
- Have the high-voltage system de-energized by a qualified person.
There is a Risk of Injury from the Engine Starting Unexpectedly
On electric - hybrid vehicles an active ready mode is difficult to
identify. Parts of the body can be clamped or pulled.
- Turn off the ignition.
- Place the ignition key outside of the vehicle interior.
Risk of Damaging the High-Voltage Cables
Misuse can damage the insulation of high-voltage cables or
high-voltage connectors.
- Never support objects on the high-voltage cables and the
high-voltage connectors.
- Never support tools on the high-voltage cables and the high-voltage
connectors.
- Never sharply bend or kink the high-voltage cables.
- When connecting pay attention to the coding of the high-voltage
connectors.
- For all procedures on vehicles with high-voltage system pay
attention to the additional warning message for these vehicles.
Refer to
→ Chapter "Warnings when Working on Vehicles with High Voltage
System".
- If procedures are necessary near components of the
high-voltage system "perform a visual inspection of the damage
of the high-voltage components and lines". Refer to
→ Chapter "Performing a Visual Inspection of Damage to High
Voltage Components and Cables".
- If work on the components of the high-voltage system is
necessity, de-energize the high-voltage system. Refer to
→ Rep. Gr.93; High-Voltage System, De-Energizing or
→ Electrical Equipment; Rep. Gr.93; High-Voltage System,
De-Energizing.
Note
The following steps using the A/C service station (checking
pressures) on the refrigerant circuit can only be performed
while the drive ready mode is active. If necessary, restart the
high voltage system.
- Charge the vehicle battery, for example, using the Battery
Charger -VAS5904- in the battery support mode to minimize the
number of automatic starts during the test- and measuring
procedures while the ready mode is active. Refer to
→ Electrical Equipment General Information; Rep. Gr.27; Battery;
Charging the Battery and
→ Electrical Equipment; Rep. Gr.93; General Notes for Working on
the High Voltage System.
- Move the selector level into position "P", activate the
parking brake and arrange the necessary tools for testing and
measuring procedures that require the ready mode to be active or
that require the ignition to be on, so that they cannot come
into contact with the turning components in the engine and so
that they are not in the vicinity of the turning components of a
running engine.
Note
- Also move the selector lever into position "P" and activate
the parking brake for testing and measuring procedures which
require the ignition to be on, but do not require the ready mode
to be active.
- The ready mode is displayed in the Instrument Cluster
Control Module -J285- above the "powermeter". Refer to Owner's
Manual.
- Activate and deactivate the ready mode. Refer to Owner's
Manual (consult the display in the Instrument Cluster Control
Module -J285-).
- Turn off the ignition.
Note
If a malfunction occurs at only one evaporator in vehicles
with two evaporators (one evaporator in the A/C unit and the
other in the battery cooling module or in the high voltage
battery heat exchanger), also check pressures in the refrigerant
circuit, are these OK? Check the line connection between the
evaporator in question and the exit of line connection at
distribution point of refrigerant lines (for constriction or
blockage, for example in the refrigerant line restrictor to the
high voltage battery heat exchanger). If no malfunction can be
detected, discharge the refrigerant circuit and charge it with
the specified refrigerant quantity. Then check the pressures and
A/C system cooling output again; if the malfunction occurs
again, check/replace the following components: if the complaint
is only occurs at the evaporator in the A/C unit, the shut-off
valve is prematurely switched by the evaporator (for example
Hybrid Battery Refrigerant Shut-Off Valve 1 -N516- or the Heater
and A/C Unit Refrigerant Cut-Off Valve -N541-). This component
is open when it is not activated and allows the refrigerant to
flow through. Replace the expansion valve on the evaporator in
the A/C unit, if no fault can be found on the Hybrid Battery
Refrigerant Shut-Off Valve 1 -N516-/Heater and A/C Unit
Refrigerant Cut-Off Valve -N541-. If a malfunction occurs only
on the evaporator for the cooling the high voltage components
(for example in the battery cooling module), check the
activation of the Hybrid Battery Refrigerant Shut-Off Valve 2
-N517- on the evaporator expansion valve in the battery cooling
module (it is closed when it is not activated and does not allow
the refrigerant to flow through). If the malfunction only occurs
on the high voltage battery heat exchanger, check the High
Voltage Battery Heater Core Refrigerant Cut-Off Valve -N542- (it
is open when it is not activated and allows the refrigerant to
flow through) and the restrictor installed in the refrigerant
line. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; System
Overview - Refrigerant Circuit (vehicle-specific
repair manual).
- With the ignition switched off, check the pressure in the
refrigerant circuit (using the service station). Refer to
→ Chapter "Refrigerant Circuit, Checking Pressure with Service
Station".
The pressures with the ignition turned off meet the
specifications.
- Charge the vehicle battery, for example, using the Battery
Charger -VAS5904- in the battery support mode to minimize the
number of automatic starts during the test- and measuring
procedures while the ready mode is active. Refer to
→ Electrical Equipment General Information; Rep. Gr.27; Battery;
Charging the Battery and
→ Electrical Equipment; Rep. Gr.93; General Notes for Working on
the High Voltage System.
Note
- Also move the selector lever into position "P" and activate
the parking brake for testing and measuring procedures which
require the ignition to be on, but do not require the ready mode
to be active.
- The engine must not be running when checking the pressures
in the refrigerant circuit on vehicles with a high voltage
system.
- The ready mode is displayed in the Instrument Cluster
Control Module -J285- above the "power meter". Refer to Owner's
Manual.
- Activate the ready mode (and observe the display in the
Instrument Cluster Control Module -J285-). Refer to the Owner's
Manual.
- Activate the drive ready mode. Refer to the Owner's Manual.
- Switch on the A/C system.
- Observe the pressure gauge of the service station.
Note
- The activation of the electrically driven A/C compressor
occurs from the vehicle electrical system. The engine RPM does
not have any effect on the A/C cooling output.
- The A/C compressor is not actuated at the maximum specified
speed (of approximately 8500/min) on a stationary or slow moving
vehicle (up to a speed of approximately 45km/h) (the A/C
compressor speed is limited to approximately 5000/min).
- The activation of the electrically driven A/C compressor can
be monitored by the "Guided Fault Finding" using the Vehicle
Diagnostic Tester Function for A/C System and the Battery
Regulation.
- Pressures must be measured at service connections; component
locations of these connections are vehicle-specific. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; System
Overview - Refrigerant Circuit (vehicle-specific
repair manual).
Specified Values for the Refrigerant Circuit Pressures
Note
On vehicles with a high-voltage system but without a heat
pump (for example on Audi A3 e-tron, Audi Q5 hybrid, Audi A6
hybrid and Audi A8 hybrid) no check valves are installed in the
refrigerant circuit. On these vehicles valves are installed in
the refrigerant circuit which regulate the flow of the
refrigerant to the evaporator (in the heater and A/C unit) or to
the heat exchanger for the cooling of the components of the
high-voltage system. These valves only have two operating
conditions (open or closed). Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit and refer to the
→ Vehicle Diagnostic Tester in the "Guided Fault Finding"
function A/C system and battery control.
High-Pressure Side:
Increasing from initial pressure (when connecting the
pressure gauges) to a maximum of 20 bar (290 psi).
Low-Pressure Side:
Decreasing from initial pressure (when connecting the
pressure gauges) to a value between 1.5 and 2.3 bar (21.7 and
33.35 psi) absolute pressure (depending on the required cooling
output).
A/C Compressor Speed:
Depending on the required cooling output between 800 and
8600/min (currently a maximum of 5000/min for parked vehicles).
Note
- The temperature of the air after the evaporator, the current
A/C compressor speed and the pressure of the refrigerant on the
high pressure side are displayed depending on the vehicle as the
measured value from the different control modules (for example
the display control head, the Climatronic Control Module -J255-,
the Front A/C Display Control Head -E87-, the Thermal Management
Control Module -J1024- etc.). Use the Vehicle Diagnostic Tester
in the "Guided Fault Finding" function of the A/C system. Refer
to
→ Wiring diagrams, Troubleshooting & Component locations.
- If a high cooling output is required (for example, a high
outside temperature and the blower speed set on high), then the
A/C compressor will not bring the pressure on the low pressure
side to the required value (for example, for a certain time
after turning on the A/C). The A/C compressor is not actuated at
the maximum specified speed (of approximately 8500/min) on a
stationary or slow moving vehicle (up to a speed of
approximately 45km/h) (the A/C compressor speed is limited to
approximately 5000/min). After a vehicle reaches a speed of more
than approximately 45 km/h, the limit for the maximum
permissible A/C compressor speed is lifted. At a A/C compressor
speed of 5000/min, a high outside temperature and a high fresh
air blower speed (inefficient environmental controls), the A/C
compressor output (the delivery volume) is no longer sufficient
to reduce the pressure on the low pressure side to the target
value. To check the A/C compressor control under these
conditions, for example, the fresh air blower is controlled only
with approximately 40% of the maximum voltage, check the
pressures at a lower fresh air blower speed. Use the Vehicle
Diagnostic Tester in the "Guided Fault Finding" Function for A/C
System and the Battery Regulation and the
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output
(vehicle-specific repair manual).
- Under unfavorable conditions (very high ambient
temperatures, high humidity), pressure on high-pressure side may
increase to max. 29 bar (421 psi).
- The specified rpm of the A/C compressor is displayed as the
measured value of the different control modules depending on the
vehicle (for example from the display control head, the
Climatronic Control Module -J255-). Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" function of the A/C system.
Refer to
→ Wiring diagrams, Troubleshooting & Component locations.)
- The measured high pressure of the respective sensor (for
example from the A/C Pressure/Temperature Sensor -G395- or by
the Refrigerant Circuit Pressure Sensor -G805-) is displayed as
a measured value from the respective control module (for example
from the Climatronic Control Module -J255- display control
head). Use the Vehicle Diagnostic Tester in the "Guided Fault
Finding" function for the air conditioner. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output
(vehicle-specific repair manual).
- The low pressure settles depending on the A/C compressor
speed and the control characteristic of the expansion valve
within the compressor output range in tolerance range (1.5 to
2.3 bar (22 to 33 psi) positive pressure).
- The target speed for the A/C compressor must be greater than
1500/min for this test.
- In setting "maximum cooling output" the target speed is
regulated to approximately 4000 up to 5000/min. This value is
vehicle-specific and is displayed as a measured value of the
respective control module (for example the Climatronic Control
Module -J255-) display and control head. Use the Vehicle
Diagnostic Tester in the "Guided Fault Finding" Function for A/C
System and Battery Regulator.
- At absolute pressure, 0 bar/psi corresponds to absolute
vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi)
absolute pressure. On the scales of most pressure gauges, 0 bar/psi
corresponds to an absolute pressure of 1 bar (14.5 psi) (can be
seen from -1 bar (-14.5 psi) mark below 0). Use the Vehicle
Diagnostic Tester in the "Guided Fault Finding" Function for A/C
System and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output
(vehicle-specific repair manual).
- If, on a vehicle with two evaporators (for example on a Audi
A8 hybrid, one in the A/C unit and one for cooling the
high-voltage components, for example, in the battery cooling
module or the high-voltage battery heat exchanger as in the Audi
A3 e-tron), the measured temperature on one evaporator
corresponds to the specified value or the specified value falls
short, but does not reach the required specified value on the
other evaporator, the following adjustment is performed: the
responsible control module (the Battery Regulation Control
Module -J840- or the Climatronic Control Module -J255-)
activates the Electrical A/C Compressor -V470- with increased
speed via various other control modules (for example, the
Electric Drive Power and Control Electronics -JX1- and the A/C
Compressor Control Module -J842-). Thereby increasing the A/C
cooling output and decreasing the pressure on the low pressure
side as well as the evaporator temperature. If the specified
value for the temperature falls short at one evaporator, the
relevant control module (for example the Battery Regulation
Control Module -J840- or the Climatronic Control Module -J255-)
activates the installed shut-off valves (Hybrid Battery
Refrigerant Shut-Off Valve 1 -N516-, Heater and A/C Unit
Refrigerant Cut-Off Valve -N541-, Hybrid Battery Refrigerant
Shut-Off Valve 2 -N517- or High Voltage Battery Heater Core
Refrigerant Cut-Off Valve -N542-) so that the evaporator which
is too cold is no longer supplied with refrigerant. Use the
Vehicle Diagnostic Tester in the "Guided Fault Finding" Function
for A/C System and refer to
→ Wiring diagrams, Troubleshooting & Component locations
and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output
(vehicle-specific repair manual).
- Since the evaporator for cooling the high-voltage components
output (in the battery cooling module and in the high-voltage
battery heat exchanger) is essential for the evaporator output
in the A/C unit, the required target temperature may still be
reached in the evaporator for cooling the high-voltage battery
with too little refrigerant in the refrigerant circuit, but the
target temperature in the A/C unit evaporator will no longer be
attainable (even though the A/C compressor is activated with
increased A/C unit speed).
Note
Read the supporting information.
Note
- If no fault is found with this malfunction,
clean the refrigerant circuit (flush using refrigerant R134a.Refer
to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a"; or blow through using compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen"). One of these malfunctions may arise due to a
constriction or a blockage in the refrigerant circuit.
- Check, depending on the vehicle, the sensor measured values for the
Evaporator Vent Temperature Sensor -G263- and, if equipped, the
Temperature Sensor before Hybrid Battery Evaporator -G756- and the
Temperature Sensor after Hybrid Battery Evaporator -G757- as well as the
A/C compressor activation via the respective control modules (for
example the A/C Compressor Control Module -J842- by the Battery
Regulation Control Module -J840- or the Climatronic Control Module
-J255- A/C control head. Use the Vehicle Diagnostic Tester in "Guided
Fault Finding" function for A/C System and the Battery Regulation. Refer
to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Wiring diagrams, Troubleshooting & Component locations.
- If there is an error in the measured value of the Evaporator Vent
Temperature Sensor -G263- (or, for example, the Temperature Sensor
before Hybrid Battery Evaporator -G756- or the Temperature Sensor after
Hybrid Battery Evaporator -G757-), this can lead to problems in the
cooling output or the evaporator in the A/C unit can freeze up. Refer to
the
→ Vehicle Diagnostic Tester "Guided Fault Finding" function for the A/C
system and the Battery Regulation and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit.
- If A/C system operation is not OK i.e. after repeating the test, for
example after replacing expansion valve (reinstalling the old expansion
valve), clean the refrigerant circuit (flush using the refrigerant
R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a" or blow through using the compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen". Then replace the A/C compressor and receiver/dryer
or dryer cartridge.
- With a malfunction on one of the temperature sensors, the evaporator
may ice up even though the quantity of refrigerant in the circuit is OK.
- If the expansion valve on the evaporator in the A/C unit (or
depending on the vehicle for example the Hybrid Battery Refrigerant
Shut-Off Valve 1 -N516-/Heater and A/C Unit Refrigerant Cut-Off Valve
-N541-) is faulty (constantly closed or does not open far enough), the
A/C compressor is actuated to maximum output and the low pressure drops
to value in graph or below (A/C compressor draws off refrigerant from
low-pressure side). Since the refrigerant cannot flow via the expansion
valve, the cooling output is not attained, high pressure may also not
increase or only increase slightly due to the absence of energy. Use the
Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the
A/C System and the Battery Regulation. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- The evaporator in the A/C system has more output than the evaporator
for cooling the high-voltage components (depending on the vehicle for
example in the battery cooling module or in the high-voltage battery
heat exchanger). The shut-off valve ( depending on the vehicle for
example the Hybrid Battery Refrigerant Shut-Off Valve 2 -N517- on the
expansion valve in the battery cooling module or the High-Voltage
Battery Heater Core Refrigerant Shut-Off Valve -N542-) is currently only
activated from or up to a certain battery temperature by the Battery
Regulation Control Module -J840- or by the Climatronic Control Module
-J255- A/C display and control head depending on the cooling version of
the Electric Vehicle Battery -A2-/Hybrid Battery Unit -AX1- (hybrid
battery), so that the energy via the evaporator for cooling the
high-voltage components (in the battery cooling module or in the
high-voltage battery heat exchanger) does not or only slightly
increases. Use the Vehicle Diagnostic Tester in the "Guided Fault
Finding" for the A/C System and Battery Control. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output.
Note
- On a vehicle with a battery cooling module, to cool the Electric
Vehicle Battery -A2- (hybrid battery), for example the Hybrid Battery
Refrigerant Shut-Off Valve 2 -N517- is currently activated by the
Battery Regulation Control Module -J840- after a specific battery
temperature is reached. If the A/C system driver is not already
activated at this time, the Electrical A/C Compressor -V470- is
activated via the A/C Compressor Control Module -J842- by the Battery
Regulation Control Module -J840-. The temperature of the air in front of
and behind the evaporator in the battery cooling module is determined by
the Battery Regulation Control Module -J840-. If it can be determined
that there is insufficient cooling, the information will be saved in the
Battery Regulation Control Module -J840-. Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" Function for the A/C System, the
A/C Compressor and the Battery Regulation.
- On a vehicle with a battery cooling module, the temperature of the
air (as well as the evaporator cooling output) in the battery cooling
module is determined via the installed temperature sensor (it currently
cannot be measured using a thermometer while operating) and may only be
checked using the Guided Fault Finding. Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" Function for the A/C System, the
A/C Compressor and the Battery Regulator. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit
- On a vehicle with a battery cooling module pay attention to the
additional notes.
- On a vehicle with a high-voltage battery heat exchanger depending on
the vehicle (for example on an Audi A3 e-tron, on other vehicles the
name of the components can vary) for cooling the high-voltage battery
(for example the Electric Vehicle Battery -A2-, the High-Voltage Battery
Charger Control Module -J1050- etc.) the High-Voltage Battery Heater
Core Refrigerant Shut-Off Valve -N542- from a specified temperature of
the control head, the Climatronic Control Module -J255- is no longer
activated (the High-Voltage Battery Heater Core Refrigerant Shut-Off
Valve -N542- is open without power). If the A/C system driver is not
already activated at this time, the Electrical A/C Compressor -V470- is
activated via the A/C Compressor Control Module -J842- from the
Climatronic Control Module -J255- control head. So that the high-voltage
battery is actually cooled by the coolant, additionally further
components of the circuit must be activated (for example the Engine
Coolant Circulation Pump 2 -V178- and the Solenoid Valve 1 -N88-) and
coolant must be flowing through the high-voltage battery heat exchanger.
If it can be determined that the cooling of the high-voltage battery is
not sufficient, this is saved in the different control modules. Use the
Vehicle Diagnostic Tester in the "Guided Fault Finding" Function of the
A/C System, the A/C Compressor and the Battery Regulation. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Rep. Gr.19; Cooling System/Coolant; Connection Diagram - Coolant Hoses.
- If no fault is found with this malfunction, clean the refrigerant
circuit (flush using refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a"; or blow through using compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen"). One of these malfunctions may arise due to a
constriction or a blockage in the refrigerant circuit.
Note
- If the A/C system function is not OK when the test is repeated,
replace the expansion valve and receiver/dryer (and the Hybrid Battery
Refrigerant Shut-Off Valve 1 -N516-/Heater and A/C Unit Refrigerant
Cut-Off Valve -N541-, if equipped). Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit.
- With this malfunction, evaporator may ice up although the quantity
of refrigerant in circuit is OK.
- If the expansion valve on the evaporator in the A/C unit or the
shut-off valve (for example the Hybrid Battery Refrigerant Shut-Off
Valve 1 -N516-/Heater and A/C Unit Refrigerant Cut-Off Valve -N541-) is
faulty (constantly closed or does not far enough), the A/C compressor is
actuated to maximum output and the low pressure drops to the specified
value or below (A/C compressor draws off refrigerant from low-pressure
side). Since no (or little) refrigerant can flow via the expansion valve
(or the corresponding shut-off valve), the cooling output is not
attained, high pressure may not increase or only increase slightly due
to the absence of energy. Use the Vehicle Diagnostic Tester in the
"Guided Fault Finding" function for the A/C System and the Battery
Regulation. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- If, in a vehicle with a battery cooling module, the expansion valve
on the evaporator in the battery cooling module is faulty (or if the
function or activation of the Hybrid Battery Refrigerant Shut-Off Valve
2 -N517- is malfunctioning), constantly closed or does not open enough,
then the A/C compressor is also activated with the maximum output (the
required temperatures in the battery cooling module are not attained).
The pressure on the low pressure side only falls to the specified value
or lower when there is no cooling output requested at the same time in
the A/C unit (the shut-off valve in front of the evaporator in the A/C
unit for example the Hybrid Battery Refrigerant Shut-Off Valve 1 -N516-
is activated and is closed). The A/C compressor extracts the refrigerant
from the low pressure side from both evaporators). Since, however, no
refrigerant can flow over the expansion valve in the A/C unit (for
example the Hybrid Battery Refrigerant Shut-Off Valve 1 -N516-) and the
cooling output in the battery cooling module is not attained (there is a
malfunction in the battery cooling module), the electrical A/C
compressor will be activated with a higher speed. Since, however, none
of the refrigerant can flow through, the pressure on the low pressure
side falls below the target value. In addition, the high pressure may
never or only slightly increase, due to the absence of energy. Use the
Vehicle Diagnostic Tester in the "Guided Fault Finding" Function for the
A/C System and the Battery Controls. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- If, on a vehicle with a high-voltage battery heat exchanger, the
restrictor installed in the refrigerant line to the high-voltage battery
heat exchanger is plugged or the shut-off valve (for example the
High-Voltage Battery Heater Core Refrigerant Shut-Off Valve -N542- on
the Audi A3 e-tron) installed in this line is faulty, constantly closed
or does not open wide enough, then the A/C compressor is also activated
with the maximum output (the required temperatures in the battery
cooling module are not attained). The pressure on the low pressure side
only falls to the specified value or lower when there is no cooling
output requested at the same time in the A/C unit (the Heater and A/C
Unit Refrigerant Cut-Off Valve -N541- for example on the Audi A3 e-tron
is activated and is closed). The A/C compressor extracts the refrigerant
from the low pressure side from both evaporators). Since, however, no
refrigerant can flow over the expansion valve in the A/C unit (via the
shut-off valve for example the Heater and A/C Unit Refrigerant Cut-Off
Valve -N541-) and the cooling output in the high-voltage battery heat
exchanger is not attained, the electrical A/C compressor is activated
with a higher speed. Since, however, none of the refrigerant can flow
through, the pressure on the low pressure side falls below the target
value. In addition, the high pressure may never or only slightly
increase, due to the absence of energy. Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" Function for the A/C System and the
Battery Controls. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual). The same also applies when a malfunction occurs in the
coolant circuit in which the high-voltage battery heat exchanger is
installed (for example the Engine Coolant Circulation Pump 2 -V178- or
the Solenoid Valve 1 -N88- on the Audi A3 e-tron are not correctly
activated or are faulty). The high-voltage battery heat exchanger is
then cooled but the cooled coolant does not reach the high-voltage
components. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant Circuit
and
→ Rep. Gr.19; Cooling System/Coolant; Connection Diagram - Coolant Hoses.
- Since the evaporator output for cooling the high-voltage components
output is smaller than the evaporator output in the A/C unit, the
required specified temperature may still be reached in the evaporator
for cooling the high-voltage battery with too little refrigerant in the
circuit, but the specified temperature in the A/C unit evaporator will
no longer be attainable (even though the A/C compressor is activated
with increased speed).
- If there is too much refrigerant oil in the circuit, the compressor
must be drained (flushed) and the receiver/dryer or dryer cartridge must
be replaced. After cleaning the refrigerant circuit (flushing with
refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a"; or blowing through using compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen"), the correct quantity of refrigerant oil is filled
into the circuit (in the A/C compressor). Refer to
→ Chapter "Approved Refrigerant Oils and Capacities".
Note
- It is not initially necessary to clean the refrigerant circuit
(flush using refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a" or blow through using compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen" when this problem occurs since normally there is
only a small quantity of moisture in the system which can be removed by
lengthy evacuation.
- If a problem involving moisture in refrigerant circuit only occurs
after a lengthy operating period or only infrequently (low pressure
drops below specification and evaporator ices up), it is sufficient to
replace the dryer installed in receiver/dryer (adjust quantity of
refrigerant oil). Refrigerant circuit is then to be evacuated for at
least three hours.
- With this malfunction, evaporator may ice up although the quantity
of refrigerant in circuit is OK.
- Likewise, the refrigerant circuit may become iced if there is a
malfunction on the Evaporator Vent Temperature Sensor -G263- or/and on
the Temperature Sensor after Hybrid Battery Evaporator -G757- (depending
on the vehicle). For these concerns also pay attention to the measured
value of the Evaporator Vent Temperature Sensor -G263- and the
Temperature Sensor after Hybrid Battery Evaporator -G757- (for example
on vehicles with a battery cooling module). Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" function. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
Note
- For the malfunction "high pressure normal, low pressure too low",
note the following: With this malfunction, evaporator in the air
conditioner may ice up although the quantity of refrigerant in circuit
is OK.
- If there is a fault in the A/C compressor ( the A/C compressor is
activated by the A/C Compressor Control Module -J842- at too high of a
speed), it is not necessary to clean the refrigerant circuit (with
refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a" or blow through it with compressed air and nitrogen.
Refer to
→ Chapter "Refrigerant Circuit, Flushing with Compressed Air and
Nitrogen". In this case, it is sufficient to replace the A/C
compressor (observe quantity of refrigerant oil in A/C compressor and if
necessary adjust).
- If, on a vehicle with a battery cooling module, the expansion valve
for the A/C unit evaporator or the expansion valve for the evaporator in
the battery cooling module is faulty (constantly closed or does not far
enough), the A/C compressor is also actuated to maximum output and the
pressure on the low pressure side drops to value in graph or below (A/C
compressor draws off refrigerant from low-pressure side). Since the
refrigerant cannot flow via the faulty expansion valve, the cooling
output in the downstream evaporator is not attained and the high
pressure may also not increase or only increase slightly due to the
absence of energy. The A/C compressor may thereby be activated with a
higher speed since the required cooling output is not attained in an
evaporator. The same also applies if the function and the activation of
a shut-off valve (for example the Hybrid Battery Refrigerant Shut-Off
Valve 1 -N516- or the Hybrid Battery Refrigerant Shut-Off Valve 2
-N517-, depending on the vehicle) is faulty. Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" function, and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- If, on a vehicle with a high-voltage battery heat exchanger, the
expansion valve for the evaporator in the A/C unit is faulty (constantly
closed or does not open far enough), or the restrictor in the
refrigerant line to the high-voltage battery heat exchanger is plugged,
the A/C compressor is also actuated to maximum output and the pressure
on the low pressure side drops to value in graph or below (A/C
compressor draws off refrigerant from the low-pressure side). Since the
refrigerant cannot flow via the faulty expansion valve or the plugged
restrictor, the cooling output in the downstream evaporator is not
attained and the high pressure may also not increase or only increase
slightly due to the absence of energy. The A/C compressor may thereby be
activated with a higher speed since the required cooling output is not
attained in an evaporator. The same also applies for the function and
the activation of a shut-off valve (for example the Heater and A/C Unit
Refrigerant Shut-Off Valve -N541-, or the High-Voltage Battery Heater
Core Refrigerant Shut-Off Valve -N542-, depending on the vehicle) or one
of the components installed in the coolant circuit for the high-voltage
components (for example the Engine Coolant Circulation Pump 2 -V178- or
the Solenoid Valve 1 -N88- on the Audi A3 e-tron, depending on the
vehicle). Use the Vehicle Diagnostic Tester in the "Guided Fault
Finding" Function for A/C System. Refer to
→ Rep. Gr.19; Cooling System/Coolant; Connection Diagram - Coolant Hoses
and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit
(vehicle-specific repair manual).
- Check the measured values of the Evaporator Vent Temperature Sensor
-G263- (and if equipped the measured values of the Temperature Sensor
Before Hybrid Battery Evaporator -G756- and the Temperature Sensor after
Hybrid Battery Evaporator -G757-, depending on the vehicle) as well as
the activation of the A/C compressor from the Battery Regulation Control
Module -J840- or from the control head of the A/C system, the
Climatronic Control Module -J255- or from the Front A/C Display Control
Head -E87- or from the Thermal Management Control Module -J1024-
(depending on the vehicle). If the measured value of the Evaporator Vent
Temperature Sensor -G263- (the Temperature Sensor Before Hybrid Battery
Evaporator -G756- or the Temperature Sensor after Hybrid Battery
Evaporator -G757-, depending on the vehicle) or the activation of the
A/C compressor faulty, the evaporator can freeze-up or the required
cooling output is not reached. Use the Vehicle Diagnostic Tester in the
"Guided Fault Finding" function of the A/C system, and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
Note
- This fault may also be caused by too much refrigerant oil in the
circuit. Overfilling with refrigerant oil can occur if, for example, the
compressor has been replaced without adjusting the quantity of
refrigerant oil.
- If, on a vehicle with a battery cooling module, the expansion valve
for the A/C unit evaporator or the expansion valve for the evaporator in
the battery cooling module is faulty (constantly closed or does not far
enough), the A/C compressor is also actuated to maximum output and the
pressure on the low pressure side drops to value in graph or below (A/C
compressor draws off refrigerant from low-pressure side). Since the
refrigerant cannot flow via the faulty expansion valve, the cooling
output in the downstream evaporator is not attained and the high
pressure may also not increase or only increase slightly due to the
absence of energy. The A/C compressor may thereby be activated with a
higher speed since the required cooling output is not attained in an
evaporator. The same also applies if the function and the activation of
a shut-off valve (for example the Hybrid Battery Refrigerant Shut-Off
Valve 1 -N516- or the Hybrid Battery Refrigerant Shut-Off Valve 2
-N517-, depending on the vehicle) is faulty. Use the Vehicle Diagnostic
Tester in the "Guided Fault Finding" function. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit
(vehicle-specific repair manual).
- If, on a vehicle with a high-voltage battery heat exchanger, the
expansion valve for the evaporator in the A/C unit is faulty (constantly
closed or does not open far enough), or the restrictor in the
refrigerant line to the high-voltage battery heat exchanger is plugged,
the A/C compressor is also actuated to maximum output and the pressure
on the low pressure side drops to value in graph or below (A/C
compressor draws off refrigerant from the low-pressure side). Since the
refrigerant cannot flow via the faulty expansion valve or the plugged
restrictor, the cooling output in the downstream evaporator is not
attained and the high pressure may also not increase or only increase
slightly due to the absence of energy. The A/C compressor may thereby be
activated with a higher speed since the required cooling output is not
attained in an evaporator. The same also applies for the function and
the activation of the Heater and A/C Unit Refrigerant Shut-Off Valve
-N541-, the High-Voltage Battery Heater Core Refrigerant Shut-Off Valve
-N542-, (for example on the Audi A3 e-tron) or one of the components
installed in the coolant circuit for the high-voltage components (for
example the Engine Coolant Circulation Pump 2 -V178- or the Solenoid
Valve 1 -N88- on the Audi A3 e-tron). Use the Vehicle Diagnostic Tester
in the "Guided Fault Finding" Function for A/C System. Refer to
→ Rep. Gr.19; Cooling System/Coolant; Connection Diagram - Coolant Hoses
and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit
(vehicle-specific repair manual).
Note
- Overfilling with refrigerant oil can occur if, for example, the
compressor has been replaced without adjusting the quantity of
refrigerant oil.
- If, for example, the expansion valve in the evaporator in the air
conditioner is faulty (permanently open), the evaporator temperature (in
the A/C unit) is no longer regulated such that only refrigerant leaves
the evaporator in a gaseous state. Under certain usage conditions,
liquid droplets may then be drawn in by the compressor and cause noise
(liquid cannot be compressed).
- If there is too much refrigerant oil in the circuit, the compressor
must be drained and the receiver/dryer must be replaced. After cleaning
the refrigerant circuit (for flushing with refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a"), fill the refrigerant circuit with the correct
quantity of refrigerant. Refer to
→ Chapter "Approved Refrigerant Oils and Capacities".
Refrigerant Circuit Pressures Specified Values, Vehicles with Heat Pump
Note
- On vehicles with a high-voltage system and heat pump (for
example on the Audi Q7 e-tron) installed in the refrigerant
circuit and electrically activated vehicles which regulate the
flow of the refrigerant in the refrigerant circuit depending on
the current operating condition. There are different versions of
these valves. Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit and use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function.
- On vehicles with the "heat pump" function and/or "high-voltage battery cooling" in not all operating conditions
is the A/C system high pressure on the service connection of the
high pressure side. The refrigerant circuit pressure on the high
pressure side can on these vehicles depending on the operating
conditions of the A/C system, can only be measured via the
pressure/temperature sensor installed in the refrigerant
circuit. Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit and the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function.
- On these vehicles the refrigerant circuit of the A/C system
is used not only to cool the vehicle interior but also to cool
the Hybrid Battery Unit -AX1- (via the refrigerant circuit for
the high-voltage system) and to heat the vehicle interior (at
low ambient temperature) via the heat pump function. So that
this function can be driven the different valves pressure and
temperature sensors as well as the pumps in the refrigerant
circuit and in the refrigerant circuit of the high-voltage
system must be installed correctly and function correctly. Refer
to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit, use the
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function and
→ Engine Mechanical; Rep. Gr.19; Cooling System/Coolant;
Coolant, Draining and Filling.
- To determine the possible cause of a malfunction, the basic
setting of the Thermal Management Control Module -J1024-
different routines are stored, which activate these functions
"Cooling the A/C system", "heat pump", and "Cooling the
components of the high-voltage system" in the Vehicle Diagnostic
Tester
→ Vehicle diagnostic tester "Guided Fault Finding"
function.
High-pressure side:
Increasing from initial pressure (when connecting the
pressure gauges) to a maximum of 20 bar.
Note
Depending on the layout of the high pressure side service
connection and the operating condition the high pressure side
can only be measured via the pressure/temperature sensor
installed in the refrigerant circuit. Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit.
Low-pressure side:
Decreasing from initial pressure (when connecting the
pressure gauges) to a value between 1.5 and 2.3 bar absolute
pressure (depending on the required cooling output).
A/C compressor speed:
Depending on the required cooling output between 800 and
8600/min (currently a maximum of 5000/min for parked vehicles).
Note
- The temperature of the air after the evaporator, the current
A/C compressor speed and the pressure of the refrigerant on the
high pressure side, are displayed as the measured value
depending on the vehicle of the different control modules (for
example from the Thermal Management Control Module -J1024-, from
the Front A/C Display Control Head -E87- or from the Climatronic
Control Module -J255-). Refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit, use the
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function.
- If a high cooling output is required (for example, a high
outside temperature and the blower speed set on high), then the
A/C compressor will not bring the pressure on the low pressure
side to the required value (for example, for a certain time
after turning on the A/C). The A/C compressor is not actuated at
the maximum specified speed (of approximately 8500/min) on a
stationary or slow moving vehicle (up to a speed of
approximately 45km/h) (the A/C compressor speed is limited to
approximately 5000/min). After a vehicle reaches a speed of more
than approximately 45 km/h, the limit for the maximum
permissible A/C compressor speed is lifted. At a A/C compressor
speed of 5000/min, a high outside temperature and a high fresh
air blower speed (inefficient environmental controls), the A/C
compressor output (the delivery volume) is no longer sufficient
to reduce the pressure on the low pressure side to the target
value. To check the A/C compressor control under these
conditions, for example, the fresh air blower is controlled only
with approximately 40% of the maximum voltage, check the
pressures at a lower fresh air blower speed. Use the Vehicle
Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function for A/C system and the battery regulation and
the
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output.
- Under unfavorable conditions (very high ambient
temperatures, high humidity), pressure on high-pressure side may
increase to max. 29 bar.
- The specified speed of the A/C compressor is displayed and
the measured value for example from the Thermal Management
Control Module -J1024- using the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function.
- The refrigerant circuit pressure (low or high pressure)
measured from the different pressure/temperature sensors
depending on the respective operating condition is displayed as
the measured value from the respective control module. Use the
Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function and refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit.
- The low pressure settles depending on the A/C compressor
speed and the control characteristic of the expansion valve (on
the evaporator of the front heater and A/C unit) within the
compressor output range in tolerance range (1.5 to 2.3 bar
positive pressure).
- The target speed for the A/C compressor must be greater than
1500/min for this test.
- In setting "maximum cooling output" the target speed is
regulated to approximately 4000 up to 5000/min. This value is
vehicle-specific and is displayed and the measured value of the
respective control module using the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function.
- At absolute pressure, 0 bar corresponds to absolute vacuum.
Normal ambient pressure corresponds to 1 bar absolute pressure.
0 bar pressure corresponds to an absolute pressure of 1 bar on
most pressure gauges (indicated by -1 bar below 0).
- If on a vehicle with two evaporators (one in the heater and
A/C unit and one for cooling the heater and A/C unit for example
the heat exchanger for the high-voltage battery) and two
condensers (one in the front end for the A/C system and one as
the heat exchanger for the heat pump function) depending on the
selected function on a component the measured temperature or
pressure, the specified value corresponds to another component
whose specifications are not achieved, check the activation of
the electrically activated valves installed in the refrigerant
circuit. At the same time pay attention to the pressure
distribution in the refrigerant circuit depending on the
installed check valves use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function are refer to
→ Heating, Ventilation and Air Conditioning; Rep.
Gr.87; Refrigerant Circuit; System Overview - Refrigerant
Circuit.
- For the correct A/C function it is also necessary that
depending on the selected functions of the respective heater
cores enough heat is supplied or removed. Pay attention for this
reason to the incorporation of the heater core in the respective
engine coolant circuit and the high-voltage system and the
function of the pumps and valves installed in it. Use the
Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault
Finding" function and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant
Circuit.
- Since the evaporator for cooling the high-voltage components
output (in the battery cooling module and in the high-voltage
battery heat exchanger) is smaller than the evaporator output in
the heater and A/C unit, the required target temperature may
still be reached in the evaporator for cooling the high-voltage
battery with too little refrigerant in the refrigerant circuit,
but the target temperature in the heater and A/C unit evaporator
will no longer be attainable (even though the A/C compressor is
activated with increased A/C unit speed).
Note
- To determine the possible cause of a malfunction, the basic setting
of the respective control module (for example in the Thermal Management
Control Module -J1024-) different routines are stored, which activate
these functions "Cooling the A/C system", "heat pump", and "Cooling the
components of the high-voltage system" in the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester"Guided Fault Finding" function.
- If for this concern no malfunction can be determined, check the
activation of the electrically activated valves installed in the
refrigerant circuit next. A malfunction can be determined here by
removing and checking the check valves installed in the refrigerant
circuit, if no malfunction can be determined here clean the refrigerant
circuit (flush with refrigerant R134a, a constriction or a blockage in
the refrigerant circuit can also lead to these complaints. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a".
- On vehicles with the "heat pump" function and/or "high-voltage
battery cooling" in not all operating conditions is the A/C system high
pressure on the service connection of the high pressure side. The
refrigerant circuit pressure on the high pressure side can on these
vehicles depending on the operating conditions of the A/C system, can
only be measured via the pressure/temperature sensor installed in the
refrigerant circuit. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit and the
Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function.
- Before beginning the repair work check the measured values of the
different pressure/temperature sensors installed in the refrigerant
circuit. If there is a malfunction in the measured value of a
pressure/temperature sensor tis can lead to problems in the cooling
output or the freezing-up of the evaporator in the front heater and A/C
unit. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant
Circuit; System Overview - Refrigerant Circuit, use the
Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Wiring diagrams, Troubleshooting & Component locations.
- Pay attention when checking the different functions (heat pump or
cooling the high-voltage battery) and the activation and function of the
refrigerant circuit components when are in connection with these
functions. Refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant Circuit.
- If the A/C system function is not OK after repeating the test, for
example after replacing expansion valve (reinstalling the old expansion
valve), clean the refrigerant circuit by flushing using the refrigerant
R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a". Then replace the A/C compressor and receiver/dryer or
dryer cartridge.
- With a malfunction on one of the temperature sensors, the evaporator
may ice up even though the quantity of refrigerant in the circuit is OK.
- If the expansion valve in the A/C unit evaporator or the heater and
A/C unit is malfunctioning (permanently closed or does not open
sufficiently), the A/C compressor is actuated to maximum output and the
low pressure drops to value in graph or below (compressor draws off
refrigerant from low-pressure side). Since the refrigerant cannot flow
via the expansion valve, the cooling output is not attained, high
pressure may also not increase or only increase slightly due to the
absence of energy. Use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00 ; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- The evaporator in the heater and A/C unit has a larger output than
the evaporator for cooling the high-voltage battery. The expansion valve
in front of this evaporator (the heat exchanger for the cooling of the
components of the high-voltage system) is activated depending on the
version to cool the Electric Vehicle Battery - A2-/Hybrid Battery Unit
-AX1- (Hybrid battery) first from or through a specified battery
temperature from the respective control module, so that the absence of
energy via this evaporator is not or only slightly raised. Use the
Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output.
- If there is too much refrigerant oil in the circuit, the compressor
must be drained (flushed) and the receiver/dryer or dryer cartridge must
be replaced. After cleaning the refrigerant circuit by flushing with
refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a". Fill the refrigerant circuit with the correct
quantity of refrigerant (in the A/C compressor). Refer to
→ Chapter "Approved Refrigerant Oils and Capacities".
Note
Read the supporting information.
Note
Read the supporting information.
Note
Read the supporting information.
Note
- With this malfunction, evaporator may ice up although the quantity
of refrigerant in circuit is OK.
- If the expansion valve in the heater and A/C unit evaporator or the
installed shut-off valve is malfunctioning (permanently closed or does
not open sufficiently), the A/C compressor is actuated to maximum output
and the low pressure drops to specification or below (compressor draws
off refrigerant from low-pressure side). Since no (or little) the
refrigerant can flow via the expansion valve, the cooling output is not
attained, high pressure may also not increase or only increase slightly
due to the absence of energy. Use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00 ; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
- If the expansion valve for the evaporator for cooling the
high-voltage components is faulty (or the function and activation is
faulty) is always closed or does not open wide enough the A/C compressor
is also activated with the maximum output (the required temperatures in
the heat exchanger are not reached). The pressure on the low pressure
side only then falls to the specified value or lower when at the same
time the front heater and A/C unit no cooling output is needed. The A/C
compressor extracts the refrigerant from the low pressure side from both
evaporators. Because no refrigerant can low over the expansion valve in
the front heater and A/C unit and the cooling output in the evaporator
for cooling the high voltage battery is not reached (there is a
malfunction in the area of the evaporator for the cooling of the high
voltage battery) the electric A/C compressor is activated with a higher
speed. If not refrigerant can flow the pressure on the low pressure side
falls under the specified value, high pressure may also not increase or
only increase slightly due to the absence of energy. The same applies if
a valve in the refrigerant circuit is not OK a malfunction in the
incorporation of the evaporator for cooling the high-voltage battery in
the high-voltage system refrigerant circuit or the pump or a valve
installed there is not OK. Then the high-Voltage Battery Heat Exchanger
is cooled, but the cooled coolant reached the high-voltage battery heat
exchanger which should not be cooled. Use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant Circuit
(vehicle-specific repair manual).
Note
- First, it is not necessary to clean the refrigerant circuit
(flushing with refrigerant R134a, refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a") in case of this complaint because generally only a
small amount of moisture is in the system and this can be removed by a
long evacuation.
- If a problem involving moisture in refrigerant circuit only occurs
after a lengthy operating period or only infrequently (low pressure
drops below specification and evaporator ices up), it is sufficient to
replace the dryer installed in receiver/dryer (adjust quantity of
refrigerant oil). Refrigerant circuit is then to be evacuated for at
least three hours.
- With this malfunction, evaporator may ice up although the quantity
of refrigerant in circuit is OK.
- A malfunction on the Evaporator Vent Temperature Sensor -G263-
or/and on the pressure/temperature sensor the can lead to the
refrigerant circuit freezing-up. For this concern also pay attention to
the measured values of the different pressure/temperature sensor in the
refrigerant circuit. Use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
Note
- For the malfunction "high pressure normal, low pressure too low",
note the following: With this fault, it may be that the evaporator in
the A/C unit is icing up although the refrigerant quantity in the
circuit is OK.
- If there is a fault in the A/C compressor (the A/C compressor is
activated by the A/C Compressor Control Module -J842- at too high of a
speed), it is not necessary to clean the refrigerant circuit by flushing
with refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a". In this case, it is sufficient to replace the A/C
compressor (observe quantity of refrigerant oil in A/C compressor and if
necessary adjust).
- If the expansion valve for the evaporator for cooling the
high-voltage components is faulty (or the function and activation is
faulty) is always closed or does not open wide enough the A/C compressor
is also activated with the maximum output (the required temperatures in
the heat exchanger are not reached). The pressure on the low pressure
side only then falls to the specified value or lower when at the same
time the front heater and A/C unit no cooling output is needed. The A/C
compressor extracts the refrigerant from the low pressure side from both
evaporators. Because no refrigerant can low over the expansion valve in
the front heater and A/C unit and the cooling output in the evaporator
for cooling the high voltage battery is not reached (there is a
malfunction in the area of the evaporator for the cooling of the high
voltage battery) the electric A/C compressor is activated with a higher
speed. If not refrigerant can flow the pressure on the low pressure side
falls under the specified value, high pressure may also not increase or
only increase slightly due to the absence of energy. The same applies if
a valve in the refrigerant circuit is not OK a malfunction in the
incorporation of the evaporator for cooling the high-voltage battery in
the high-voltage system refrigerant circuit or the pump or a valve
installed there is not OK. Then the high-Voltage Battery Heat Exchanger
is cooled, but the cooled coolant reached the high-voltage battery heat
exchanger which should not be cooled. Use the Vehicle Diagnostic Tester
in the "Guided Fault Finding" function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant Circuit
(vehicle-specific repair manual).
- A malfunction on the Evaporator Vent Temperature Sensor -G263-
or/and on the pressure/temperature sensor the can lead to this concern.
Also pay attention to the measured values of the different
pressure/temperature sensor in the refrigerant circuit. Use the
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.00; Repair
Instructions; Checking Cooling Output (vehicle-specific
repair manual).
Note
- This fault may also be caused by too much refrigerant oil in the
circuit. Overfilling with refrigerant oil can occur if, for example, the
compressor has been replaced without adjusting the quantity of
refrigerant oil.
Note
- Overfilling with refrigerant oil can occur if, for example, the
compressor has been replaced without adjusting the quantity of
refrigerant oil.
- If for example the expansion valve for the evaporator in the A/C
unit or for the evaporator for cooling the high-voltage battery is
faulty (always open) the evaporator temperature (in the heater and A/C
unit) is no longer regulated that only refrigerant in gaseous state
exits from the evaporator. Under certain usage conditions, liquid
droplets may then be drawn in by the compressor and cause noise (liquid
cannot be compressed).
- If there is too much refrigerant oil in the circuit, the compressor
must be drained and the receiver/dryer must be replaced. After cleaning
the refrigerant circuit by flushing with refrigerant R134a. Refer to
→ Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant
R134a". Fill the refrigerant circuit with the correct
quantity of refrigerant. Refer to
→ Chapter "Approved Refrigerant Oils and Capacities".
Note
- If the required cooling output on the evaporator in the front heater
and A/C unit (and on the evaporator for cooling the high-voltage battery
is OK) and there is a concern due to insufficient heating performance on
the heat exchanger for the heat pump operation. The cause may be in the
high-voltage system coolant circuit or in the engine coolant circuit. If
the pumps and valves in the high-voltage system coolant circuit is not
activated correctly or its function is not OK via the evaporator (heat
exchanger) for the high-voltage system components not enough heat energy
is absorbed from the coolant. If the pumps and valves in the coolant
circuit of the engine are not started correctly or its function are not
OK via the heat exchanger for the heat pump function for absorbing the
heat energy is not transferred to the coolant flowing to the heat
exchanger in the heater and A/C unit. Use the Vehicle Diagnostic Tester
→ Vehicle diagnostic tester in the "Guided Fault Finding"
function and refer to
→ Heating, Ventilation and Air Conditioning; Rep. Gr.87; Coolant Circuit
(vehicle-specific repair manual).
READ NEXT:
Vehicles with a High Voltage System (Hybrid Vehicles)
Extremely Dangerous Due to High-Voltage
The high-voltage system is under high-voltage. Death or serious
bodily injury by electric shock.
- I
The refrigerant circuit was completely empty (for example
with larger leak or cracked hose)
Note
In the event of only a minor leak with slow escape of
refrigerant (e.g. at a small leakage
SEE MORE:
1 - Subframe
Removing and installing. Refer to
→ Chapter "Subframe, Removing and Installing".
2 - Bolt
9 Nm
3 - Bolt
20 Nm
4 - Subframe Shield
Installed depending on the engine versions
Removing and installing. Refer to
→ Chapter "
Applies to vehicles: with Convenience key
The doors and the rear lid can be unlocked and
locked without operating the master key.
Fig. 30 Door handle: locking the vehicle
Unlocking vehicle
Take hold of the door handle. The door is unlocked
automatically.
Pull the handle to open the door.
Locki