Possible deviation from specified value during the pressure test (9 Of 32)

Possible deviation from specified value during the pressure test
The requested cooling output is not attained. The high pressure and the low pressure corresponds to the specified 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 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 approximately to the specified capacity, the measured value of the Evaporator Vent Temperature Sensor -G263-, the activation of the A/C Compressor Regulator Valve -N280- and the function of the expansion valve is faulty or there is a malfunction on another component (see below). The measured value of the Evaporator Vent Temperature Sensor -G263- is faulty. -- Check the measured value and installation of the Evaporator Vent Temperature Sensor -G263-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function of the A/C system and refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM and A/C COMPRESSOR (vehicle-specific service information). The activation of the A/C Compressor Regulator Valve -N280- is faulty. -- Check the activation of the A/C Compressor Regulator Valve -N280- and if necessary service. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function of the A/C system. Expansion valve malfunctioning. If a shut-off valve installed in the refrigerant circuit does not open or opens incorrectly. Refer to REFRIGERANT CIRCUIT (vehicle-specific service information). -- Run hand over refrigerant circuit to check for differences in temperature. Refer to REFRIGERANT CIRCUIT (vehicle-specific service information). If on a component a temperature drop is determined, because the hose or pipe are kinked or constricted, replace this component. If there is a blockage or no malfunction can be determined, clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- If equipped, check the function of the installed shut-off valve. Refer to REFRIGERANT CIRCUIT (vehicle-specific service information).-- Replace the expansion valve and desiccant bag/dryer cartridge (or reservoir/receiver/dryer). Refer to COMPONENTS, REPLACING and REFRIGERANT CIRCUIT (vehicle-specific service information). Too much refrigerant oil in the refrigerant circuit -- If the extracted refrigerant quantity meets the specified capacity or is only slightly smaller than the specified capacity (maximum 100 g) (refer to TECHNICAL DATA (vehicle-specific service information) too much refrigerant oil is in the refrigerant circuit. Clean the refrigerant circuit (flush with refrigerant R1234yf) (refer to REFRIGERANT CIRCUIT, CLEANING ) fill with the correct quantity of refrigerant and refrigerant oil and repeat the test. Expansion valve malfunctioning. If a shut-off valve installed in the refrigerant circuit does not open or opens incorrectly. Refer to REFRIGERANT CIRCUIT (vehicle-specific service information). -- If equipped, check the function of the installed shut-off valve. Refer to REFRIGERANT CIRCUIT (vehicle-specific service information).-- Replace the expansion valve and desiccant bag/dryer cartridge (or reservoir/receiver/dryer). Refer to COMPONENTS, REPLACING and REFRIGERANT CIRCUIT (vehicle-specific service information).
Final Procedures
-- Charge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, CHARGING .-- Repeat the test. Refer to MECHANICALLY DRIVEN A/C COMPRESSOR, CHECKING PRESSURE WITH A/C SYSTEM SWITCHED ON .

NOTE:

Check the measured values of the Evaporator Vent Temperature Sensor -G263- and the activation of the A/C Compressor Regulator Valve -N280-. If measured value of Evaporator Vent Temperature Sensor -G263- is incorrect, evaporator may ice up or cooling output is not attained use the Vehicle Diagnostic Tester in the "Guided Fault Finding " function for the A/C system and refer to COMPONENT LOCATION OVERVIEW - A/C SYSTEM (vehicle-specific service information).

Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

If expansion valve is malfunctioning (permanently open), evaporator temperature is no longer regulated such 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 A/C compressor must be discharged and the reservoir/receiver/dryer (or dryer cartridge) replaced (if equipped). Refer to REFRIGERANT CIRCUIT (vehicle-specific service information). After cleaning the refrigerant circuit (flushing with refrigerant R1234yf refer to REFRIGERANT CIRCUIT, CLEANING ) fill it with the correct quantity of refrigerant oil in the circuit. Refer to TECHNICAL DATA (vehicle-specific service information).