Possible Deviation from Specified Value During the Pressure Test (1 Of 11)

WARNING: This page is about a different car, the 2022 Volkswagen ID.4 and 2021 Volkswagen ID.4. However, it is still accessible from the selected car via links, so may be relevant.

Possible Deviation from Specified Value During the Pressure Test
The required cooling output is not attained in the heater and A/C unit evaporator (and in the evaporator for battery cooling module). High pressure remains constant or increases only slightly (above pressure with A/C compressor stopped). Low pressure quickly drops to specified value or lower.
Possible causes for the deviation from specified value and their solutions
There is too little refrigerant in the refrigerant circuit. -- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity is significantly less than the specified capacity (more that 100 g (3.5 oz) less). Refer to Technical Data (vehicle-specific Service Information), and look for leaks and correct. Refer to LEAKS, FINDING .-- The extracted refrigerant quantity corresponds approximately to the specified capacity, check the activation of the A/C compressor and the installed shut-off valve, if not malfunction is determined, replace the expansion valve for the evaporator in the heater and A/C unit. Refer to Refrigerant Circuit (vehicle-specific Service Information). The activation of the A/C compressor (and if equipped the Refrigerant Shut-Off Valve 1 -N696- and the Refrigerant Shut-Off Valve 2 -N640-) is faulty. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation and the appropriate service information (vehicle-specific Service Information), Component Location Overview - A/C System (vehicle-specific Service Information) and A/C Compressor (vehicle-specific Service Information). -- Check the activation and function of the A/C compressor (and if equipped the shut-off valves, for example the Refrigerant Shut-Off Valve 1 -N696-, the Refrigerant Shut-Off Valve 2 -N640-) and if necessary service. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C compressor and the battery regulation. If this is OK extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING . The expansion valve for the evaporator in the heater and A/C unit is faulty. Refer to Refrigerant Circuit (vehicle-specific Service Information) for replacing. One if the Refrigerant Shut-Off Valve 1 -N696- /Refrigerant Shut-Off Valve 2 -N640- (if equipped) is faulty (closed), check the function. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation and refer to Refrigerant Circuit (vehicle-specific Service Information) for replacing. Constriction or blockage in the refrigerant circuit (for example in the refrigerant line between the "low pressure side" service connection and the A/C compressor). Refer to Refrigerant Circuit (vehicle-specific Service Information). -- If there is a blockage clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- If the hose or pipe is kinked or constricted, replace this component. Refer to Refrigerant Circuit (vehicle-specific Service Information). The expansion valve for the evaporator in the heater and A/C unit is faulty. Refer to Refrigerant Circuit (vehicle-specific Service Information) for replacing. A Refrigerant Shut-Off Valve 1 -N696- /Refrigerant Shut-Off Valve 2 -N640- is faulty (closed). Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation and refer to Refrigerant Circuit (vehicle-specific Service Information) for replacing.
Final Procedures
-- Charge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CHARGING .-- Repeat the test. Refer to ELECTRICALLY-DRIVEN A/C COMPRESSOR, CHECKING PRESSURE WITH A/C SYSTEM SWITCHED ON .

NOTE:

If for this complaint a malfunction is determined in the diagnostic, check the refrigerant circuit for a constriction or blockage (a constriction or a blockage in the refrigerant circuit can also lead to these complaints). If nothing is determined here, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .

Check the measured values of the sensors for 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 at the activation of the A/C compressor via the corresponding control module. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.

If there is an error in 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 Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation) this can lead to problems in the cooling output and the evaporator can freeze-up.

With a malfunction on one of the temperature sensors, the evaporator may ice up even though the quantity of refrigerant in the refrigerant circuit is OK.

If the A/C system function is not OK after repeating the test, for example after replacing expansion valve, clean the refrigerant circuit by flushing using the refrigerant R1234yf. Refer to REFRIGERANT CIRCUIT, CLEANING . Replace the A/C compressor and dryer cartridge (or reservoir/receiver/dryer). Refer to Refrigerant Circuit (vehicle-specific Service Information).

If the expansion valve in the heater and A/C unit evaporator or the shut-off valve is faulty (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 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 and Refrigerant Circuit (vehicle-specific Service Information).

The evaporator in the heater and A/C unit has considerably more output than the evaporator for battery cooling. Depending on the model, the Refrigerant Shut-Off Valve 2 -N640- on the expansion valve in the battery cooling module is activated for cooling the Electric Vehicle Battery -A2- (depending on the vehicle, Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function of the A/C system and the battery regulation) by the corresponding control module at a specific battery temperature (for example, by the Battery Regulation Control Module -J840-), so that the energy conversion via the evaporator for battery cooling is not or only slightly increased. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and battery regulation, and refer to Refrigerant Circuit (vehicle-specific Service Information).