Possible Deviation From Specified Value During The Pressure Test (11 Of 12)

Possible Deviation from Specified Value during the Pressure Test
High and low pressure normal The required cooling output is not attained in the heater and A/C unit evaporator (and in the evaporator for cooling the high-voltage components). or High and low pressure normal 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 cooling the high-voltage components).
Possible causes for the deviation from specified value and their solutions
One in or on the removed refrigerant circuit pressure/temperature sensor or temperature sensor sends incorrect values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Component Location Overview - A/C System . Activation of the A/C compressor is faulty. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. If one of the valves installed in the refrigerant circuit is faulty or does not work correctly. Refer to Refrigerant Circuit . Too much refrigerant in the circuit. The expansion valve for the evaporator in the front heater and A/C unit is faulty. Too much refrigerant oil in the circuit. -- Check the measured values of the different pressure/temperature sensor and temperature sensor when operating the A/C system, and replace the components with incorrect measured values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Component Location Overview - A/C System .-- Check the activation and function of the A/C compressor and service using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.-- Check the function and activation of the various valves and pressure/temperature sensors installed in the refrigerant circuit via the pressure distribution in the refrigerant circuit. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function. Refer to Refrigerant Circuit .-- If no malfunction can be determined, extract the refrigerant from the refrigerant circuit. If quantity of refrigerant extracted is substantially greater than specified capacity: -- Fill the refrigerant circuit and repeat the test. If quantity of refrigerant extracted roughly corresponds to specified capacity: -- Clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- Fill in correct quantity of refrigerant oil into circuit (see note).
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:

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 heater and 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 (flushing with refrigerant R1234yf) and fill it with the correct quantity of refrigerant oil in the circuit. Refer to REFRIGERANT CIRCUIT, CLEANING and Technical Data .

Refer to Possible Deviation From Specified Value During The Pressure Test (1 Of 12) for additional information.