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Home >> Audi >> 2021 >> A4 Quattro Premium Plus, 2.0L Eng VIN B >> Repair and Diagnosis (Single Page) >> 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 (3 Of 12)

Possible Deviation From Specified Value During The Pressure Test (3 Of 12)

Possible Deviation from Specified Value during the Pressure Test
  • High pressure normal
  • Low pressure normal or too low (less than the specified value)
  • The required cooling output is only not attained at the heater and A/C unit evaporator (the cooling output on the evaporator for cooling the high-voltage components is OK).
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 .
  • Not enough refrigerant in refrigerant circuit
  • Activation of the A/C compressor is faulty.
  • The expansion valve for the evaporator in the front heater and A/C unit is faulty.
  • The shut-off valve in front of the expansion valve for the evaporator in the front heater and A/C unit is faulty.
  • One or the other valves installed in the refrigerant circuit is faulty or does not work correctly.
-- 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 . If no errors can be detected, evacuate the refrigerant.-- 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 no malfunction is determined. Refer to Refrigerant Circuit -- 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 .-- Check the function and activation of the various valves 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 .-- Depending on the results, service the activation or replace the faulty component (shut-off valve/expansion valve). Refer to the Refrigerant Circuit .
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:

Read the supporting information. Refer to Possible Deviation From Specified Value During The Pressure Test (1 Of 12) .

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