Possible Deviation From Specified Value During The Pressure Test (4 Of 11)

Possible Deviation from Specified Value During the Pressure Test
The A/C compressor noise (particularly after switch-on) The required cooling output is not attained in the heater and A/C unit evaporator and/or in the evaporator for battery cooling. High pressure normal or too high Low pressure too high (the specified value is not reached,
Possible causes for the deviation from specified value and their solutions
Activation of function of the A/C compressor or if equipped the refrigerant shut-off valve 1 the refrigerant shut-off valve 2 is faulty. Too much refrigerant or refrigerant oil 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. If no malfunction can be determined, extract the refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- Extract refrigerant from the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, DISCHARGING .-- If the extracted refrigerant quantity is substantially greater (more than 100 g (3.5 oz)) than the specified capacity there is too much refrigerant in the refrigerant circuit. Fill the refrigerant circuit and repeat the test. Refer to Technical Data .-- If the extracted refrigerant quantity meets the specified capacity is only slightly greater than the specified capacity (maximum 100 g (3.5 oz)) too much refrigerant oil is in the refrigerant circuit. Refer to Technical Data . Clean the refrigerant circuit (flush with refrigerant R1234yf) and fill with the correct quantity of refrigerant and refrigerant oil and repeat the test. Refer to REFRIGERANT CIRCUIT, CLEANING . Expansion valve malfunctioning -- 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 Refrigerant Circuit . A/C compressor faulty -- Replace the A/C compressor. Refer to COMPONENTS, REPLACING and A/C Compressor .-- If there is dirt in the refrigerant circuit, clean the refrigerant circuit (flush with refrigerant R1234yf) and replace the expansion valve and desiccant bag/dryer cartridge (or receiver/receiver/dryer). Refer to COMPONENTS, REPLACING and REFRIGERANT CIRCUIT, CLEANING .
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 . 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 Refrigerant Circuit .