Possible Deviation from Specified Value During the Pressure Test (5 Of 11)

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). High pressure and low pressure are normal (correspond to the specified value)
Possible causes for the deviation from specified value and their solutions
Activation of function of the A/C compressor and if equipped the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2 is faulty. Not enough refrigerant in the refrigerant circuit. -- Check the activation and function of the A/C compressor and if equipped the refrigerant shut-off valve 1 the refrigerant shut-off valve 2. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function for the A/C system and the battery regulation and if necessary service. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information). If no malfunction can be determined, extract the refrigerant from 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 .-- If the extracted refrigerant quantity corresponds to the specified capacity or is only slightly smaller (maximum 100 g (3.5 oz)) the expansion valve for the evaporator or a shut-off valve installed in the heater and A/C unit is faulty. Refer to Technical Data (vehicle-specific Service Information). The expansion valve for the evaporator in the heater and A/C unit is faulty. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information). A refrigerant shut-off valves (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. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information) for replacing. -- If equipped check the function of the installed shut-off valve. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).-- Replace the expansion valve for the evaporator in the heater and A/C unit. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information). Too much refrigerant oil in the refrigerant circuit -- Clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- Replace the expansion valve for the evaporator in the A/C unit (and for the evaporator for battery cooling) as well as the desiccant bag/dryer cartridge (or receiver/receiver/dryer). Refer to COMPONENTS, REPLACING and Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).
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:

This fault may also be caused by too much refrigerant oil in the refrigerant circuit. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. Refer to COMPONENTS, REPLACING and Technical Data (vehicle-specific Service Information). If there is too much refrigerant oil in the refrigerant circuit, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .

If the expansion valve for the heater and A/C unit evaporator (or for the evaporator in the battery cooling) is faulty (permanently closed or does not open sufficiently), the A/C compressor is actuated to maximum output and the low pressure drops to the target value 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 and the high pressure may also not increase or only increase slightly due to the absence of energy. The same applies if the function or the activation of the refrigerant shut-off valve 1 or the refrigerant shut-off valve 2 is faulty. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function for the A/C system and the battery regulation. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).