Audi Q7: 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".
READ NEXT:
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
f
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
SEE MORE:
Description
Electronic Stabilization Control (ESC) supports
driver safety. It reduces the risk of slipping and
improves driving stability. ESC detects critical situations,
such as if the vehicle is oversteering or
understeering, or if the wheels are spinning.
The brakes are applied or the motor t
Component Location Overview - Control Modules
1 - Vehicle Electrical System Control Module -J519-
Removing and installing. Refer to
→ Chapter "Vehicle Electrical System Control Module -J519-, Removing and
Installing".
2 - Mount
For Vehicle Electrical System Contro