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Home >> Audi >> 2020 >> SQ8 Premium Plus >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Air Conditioning (Refrigerant R1234YF Servicing) (1 Of 2) >> 87 Air Conditioning >> Working With A/C Service Station >> Pressures, Checking >> Electrically-Driven A/C Compressor, Checking Pressure With A/C System Switched On >> Possible Deviation from Specified Value During the Pressure Test (10 Of 12)

Possible Deviation from Specified Value During the Pressure Test (10 Of 12)

Possible Deviation from Specified Value during the Pressure Test
  • High pressure normal or too high
  • Low pressure too high.
  • A/C compressor noise (particularly after switch-on)
  • The required cooling output is not attained in the front 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
  • 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 Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).
  • 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 .
  • Too much refrigerant in the circuit.
  • 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 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.
  • 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:
-- Check the activation and function of the A/C compressor and the valves installed in the refrigerant circuit (shut-off valve and expansion valve). Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function.-- Depending on the result, service the activation or replace the faulty component (shut-off valve, expansion valve, or A/C compressor as well as the receiver/dryer/dryer). Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).-- If no malfunction can be determined, there may be too much refrigerant oil in the circuit, clean the refrigerant circuit (flush with refrigerant R1234yf. Refer to 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 circuit. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

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

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