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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 (5 Of 12)

Possible Deviation From Specified Value During The Pressure Test (5 Of 12)

Possible Deviation from Specified Value during the Pressure Test
  • High pressure does not increase or only increases slightly above pressure with engine stopped.
  • Low pressure does not drop or drops only slightly.
  • The required cooling output is not attained in the heater and A/C unit evaporator (and in the evaporator for cooling the high-voltage components).
Possible causes for the deviation from specified value and their solutions
  • No activation of the A/C compressor, the A/C compressor is not driven.
  • If one of the valves installed in the refrigerant circuit is faulty or does not work correctly. 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).
-- 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 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 (A/C compressor, shut-off valve, expansion valve). Refer to the Refrigerant Circuit .-- Check the refrigerant circuit lines. If the hose or pipe is kinked or constricted, remove this component. Refer to Refrigerant Circuit .-- Run hand over refrigerant circuit to check for differences in temperature (position with a blockage). If there is a blockage clean the refrigerant circuit (flush with refrigerant R1234yf). Refer to REFRIGERANT CIRCUIT, CLEANING .-- If a malfunction is determined on the A/C compressor, replace the A/C compressor. Refer to COMPONENTS, REPLACING .-- If no malfunction can be determined 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:

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

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