Possible Deviation From Specified Value During The Pressure Test (3 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). The high pressure pipe corresponds to the specified value The low pressure is too low (lower than the target value)
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 , 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 . 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. -- If no malfunction can be determined, 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.-- Clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING . The expansion valve in the heater and A/C unit or if equipped the evaporator for battery cooling is faulty. -- Replace the expansion valve for the evaporator in the heater and A/C unit (and for the evaporator for battery cooling) as well as the desiccant bag/dryer cartridge (or receiver/receiver/dryer). 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:

For the malfunction "high pressure normal, low pressure too low" With this malfunction, evaporator may ice up, although quantity of refrigerant in circuit is OK.

If there is a malfunction an the refrigerant circuit, it was not activated and operates nevertheless, it is not necessary to clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING . For this error it is sufficient to replace the A/C compressor (pay attention to the refrigerant oil quantity in the A/C compressor). Refer to COMPONENTS, REPLACING and A/C Compressor .

If there is a fault in the A/C compressor (the A/C compressor is activated by the A/C compressor control module at too high of a speed), it is not necessary to clean the refrigerant circuit (flushing with refrigerant R1234yf). For this malfunction it is sufficient to replace the A/C compressor (pay attention to the refrigerant oil quantity in the A/C compressor). Refer to REFRIGERANT CIRCUIT, CLEANING , Technical Data and A/C COMPRESSOR .

If the expansion valve (or one of the two expansion valves) is faulty (permanently closed or does not open sufficiently), the A/C compressor is also actuated to maximum output and the pressure on the low pressure side drops to specified value or below (compressor draws off refrigerant from the 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 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 .

Check the measured values for the Evaporator Vent Temperature Sensor -G263- (and the measured values for the Temperature Sensor Before Hybrid Battery Evaporator -G756- and the Temperature Sensor After Hybrid Battery Evaporator -G757-) as well as the activation of the A/C compressor by the A/C Compressor Control Module --. If the measured value of the Evaporator Vent Temperature Sensor -G263- (the Temperature Sensor Before Hybrid Battery Evaporator -G756-, Temperature Sensor After Hybrid Battery Evaporator -G757-) or the activation of the A/C compressor is faulty, the evaporator can freeze up or the required cooling output is not read. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function for the A/C system and the battery regulation and refer to Component Location Overview - A/C System .