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Home >> Audi >> 2021 >> A4 Quattro Premium Plus, 2.0L Eng VIN B >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> A/C Compressor >> 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 (11 Of 11)

Possible Deviation From Specified Value During The Pressure Test (11 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 does not increase or only increases slightly above pressure with engine stopped.
  • The low pressure does not drop or drops only slightly.
Possible causes for the deviation from specified value and their solutions
  • No activation of the A/C compressor. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function.
  • If equipped, the refrigerant shut-off valve 1 is faulty (closed)
-- Check the activation and function of the A/C compressor (and the refrigerant shut-off valve 1, the refrigerant shut-off valve 2). Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C compressor and the battery regulation. If no malfunction can be determined replace the expansion valve on the evaporator in the heater and A/C unit. Refer to Refrigerant Circuit .
  • Constriction or obstruction in refrigerant circuit (for example, inside the refrigerant line between the service connection "low pressure side" and the A/C compressor).
-- If there is a blockage clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING . Replace the expansion valve for the evaporator in the A/C unit (and for the evaporator for battery cooling) as well as the desiccant bag/dryer cartridge (or receiver/receiver/dryer). Refer to COMPONENTS, REPLACING and Refrigerant Circuit .-- If the hose or pipe is kinked or constricted, replace this component. Refer to Refrigerant Circuit .
  • A/C compressor faulty.
-- Replace the A/C compressor. Refer to COMPONENTS, REPLACING and A/C Compressor .
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 .