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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) >> General Servicing >> Air Conditioning (Refrigerant R1234YF Servicing) (1 Of 2) >> 87 Air Conditioning >> Working With A/C Service Station >> Pressures, Checking >> Mechanically Driven A/C Compressor, Checking Pressure With A/C System Switched On >> Pressures, Checking

Pressures, Checking

Refrigerant circuit with expansion valve, receiver/dryer with or without A/C Clutch -N25- and A/C Compressor Regulator Valve -N280- (with an A/C compressor regulated from the outside)

NOTE:

Connect the A/C service station. Refer to A/C SERVICE STATION ON REFRIGERANT CIRCUIT, CONNECTING .

If a malfunction occurs at only one evaporator in vehicles with two evaporators, check pressures in the refrigerant circuit; if they are OK, check line connection between malfunctioning evaporator and line connection end at distribution point of refrigerant lines (for constrictions or blockage). If no malfunction can be determined, empty the refrigerant circuit and refill with the specified refrigerant quantity. Then check the pressures and the A/C system cooling output again; if the complaint still exists, replace the expansion valve that is prematurely switched by the questioned evaporator. Refer to Refrigerant Circuit .

Refer to REFRIGERANT CIRCUIT WITH IGNITION SWITCHED ON, CHECKING PRESSURE 

Test Requirements

NOTE:

The switching pressures for the activation of the A/C Compressor Regulator Valve -N280-, the A/C Clutch -N25- (if equipped) and the Radiator Fan -V7- are vehicle specific. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system.

Pressures must be measured at the service connections; the component location for these connections are vehicle-specific. Refer to Refrigerant Circuit .

NOTE:

If the engine is not warm perform a road test.

For the cooling output test the engine must be warm but at an ambient temperature smaller than 25 °C (77 °F) a specific A/C system cooling output it is necessary that the engine and lower ambient temperatures are warm.

-- Start the engine.

-- Adjust the A/C system to maximum cooling output. Refer to COOLING OUTPUT, CHECKING .

NOTE:

The A/C compressor is driven by different components depending on the engine (belt or input shaft). The belt pulley or the drive unit has an overload protection to protect these components and the engine, if the A/C compressor is runs with resistance. Refer to A/C Compressor .

On vehicles with A/C Compressor Regulator Valve -N280- the control current can be read out in the measured values. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function for the A/C system.

If A/C compressor is not driven with the engine running or regulating valve is not actuated:

-- Determine and eliminate cause for example by checking air conditioner DTC memory. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system.

-- If equipped, check the power supply for the A/C Clutch -N25- if this is OK, service the A/C clutch. Refer to Refrigerant Circuit .

-- Check the activation of the A/C Compressor Regulator Valve -N280-. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system.

NOTE:

On A/C compressors with a A/C Clutch -N25- the A/C compressor only works (delivers refrigerant) when near the A/C Compressor Regulator Valve -N280- the A/C Clutch -N25- is also activated. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system.

The A/C Compressor Regulator Valve -N280- (and the A/C Clutch -N25-) is activated by the A/C Control Module -J301-, from the Front A/C Display Control Head -E87- or the Climatronic Control Module -J255- or a downstream control module. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system. Refer to Refrigerant Circuit .

All of the test requirements marked with a * are vehicle-specific and described in the Service Information belonging to the vehicle. Refer to COOLING OUTPUT, CHECKING and Refrigerant Circuit .

Adjustment for example on the Front A/C Display Control Head -E87- or the Climatronic Control Module -J255- or the A/C Control Module -J301- (and the Rear A/C Display Control Head -E265- on vehicles with two heater and A/C units)*. Refer to COOLING OUTPUT, CHECKING and Component Location Overview - A/C System .

Adjustment on the Front A/C Display Control Head -E87- /Climatronic Control Module -J255- *. Refer to COOLING OUTPUT, CHECKING and Component Location Overview - A/C System .

-- Preselect "Auto" mode (A/C compressor on).

-- Set temperature pre-selector switch to "cold" or "LO" for driver's side and front passenger's side (and left and right rear seats in vehicles with two heater and A/C units).

Adjustment on the A/C Control Module -J301- *:

-- Press A/C button and Rec- or recirculated air button.

-- Turn rotary temperature control towards "cold" stop.

-- Position the fresh-air blower dial in the position "4" (maximum fresh air blower speed).

The following system test conditions should be met:

NOTE:

On specific versions the fan is switched on after the refrigerant circuit pressure specified value is exceeded. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function of the A/C system.

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