Audi A4 Owners & Service Manuals

Audi A4: Compressor, Replacing on Account of Leakage or Internal Damage

Vehicles with a High Voltage System (Hybrid Vehicles)

Extremely Dangerous Due to High-Voltage

The high-voltage system is under high-voltage. Death or serious bodily injury by electric shock.

- Individuals with electronic/medical life- and health sustaining machines in or on their person cannot perform any work on high-voltage systems. Life- and health sustaining machines are for example pain killer pumps, implanted defibrillators, pacemakers, insulin pumps, and hearing aids.

- Have the high-voltage system de-energized by a qualified person.

There is a Risk of Injury from the Engine Starting Unexpectedly

On electric - hybrid vehicles an active ready mode is difficult to identify. Parts of the body can be clamped or pulled.

- Turn off the ignition.

- Place the ignition key outside of the vehicle interior.

Risk of Damaging the High-Voltage Cables

Misuse can damage the insulation of high-voltage cables or high-voltage connectors.

- Never support objects on the high-voltage cables and the high-voltage connectors.

- Never support tools on the high-voltage cables and the high-voltage connectors.

- Never sharply bend or kink the high-voltage cables.

- When connecting pay attention to the coding of the high-voltage connectors.

  • For all procedures on vehicles with high-voltage system pay attention to the additional warning message for these vehicles. Refer to → Chapter "Warnings when Working on Vehicles with High Voltage System".
  • If procedures are necessary near components of the high-voltage system "perform a visual inspection of the damage of the high-voltage components and lines". Refer to → Chapter "Performing a Visual Inspection of Damage to High Voltage Components and Cables".
  • If work on the components of the high-voltage system is necessity, de-energize the high-voltage system. Refer to → Rep. Gr.93; High-Voltage System, De-Energizing or → Electrical Equipment; Rep. Gr.93; High-Voltage System, De-Energizing.

- Charge the vehicle battery, for example, using the Battery Charger -VAS5904- in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures while the ready mode is active. Refer to → Electrical Equipment General Information; Rep. Gr.27; Battery; Battery, Charging and → High Voltage Vehicle General Information; Rep. Gr.93; High-Voltage System General Warnings.

- For testing and measurement procedures that require the ready mode to be active or the ignition to be switched on, the selector lever must be in the "P" position and the parking brake must be activated. The required tools must be placed so that they do not come into contact with any rotating components in the engine and they must also not go into the vicinity of the rotating components when the engine is running.


  • Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures which require the ignition to be on, but do not require the ready mode to be active.
  • The ready mode is displayed in the Instrument Cluster Control Module -J285- above the "power meter". Refer to Owner's Manual.
  • For activating and deactivating the ready mode, refer to the Owner's Manual (while doing so, note the display in the Instrument Cluster Control Module -J285-).

All Vehicles

For example, because of noise or no A/C compressor output


  • If there is damage on the A/C compressor electronics, for example on the A/C Compressor Regulator Valve -N280- on a mechanically driver A/C compressor or the A/C Compressor Control Module -J842- of the electrically driven A/C compressor the refrigerant circuit does not have to always be cleaned. Here it is usually acceptable to replace the A/C compressor without cleaning the refrigerant circuit (adapt the amount of refrigerant oil). Refer to → Chapter "Compressor, Replacing without the Need for Flushing Refrigerant Circuit".
  • If a faulty A/C compressor is replaced with an A/C compressor from another manufacturer check for the A/C compressor to be installed has the same refrigerant oil approved which is already in the refrigerant circuit (from the removed A/C compressor). If a different refrigerant oil is approved for the A/C compressor to be installed then the A/C compressor which was removed, the refrigerant circuit must be flushed. Refer to → Chapter "Approved Refrigerant Oils".

- Discharge the refrigerant circuit.

- Remove the A/C compressor. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; A/C Compressor (vehicle-specific repair manual).

- Clean the refrigerant circuit (flush with Refrigerant R134a). Refer to → Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant R134a" .


  • For internal damage (to the A/C compressor) check the refrigerant hoses and condenser for example shavings have penetrated clean refrigerant hoses and condenser (flush with refrigerant R134a. Refer to → Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant R134a" and if necessary replace the refrigerant hoses.
  • In vehicles with two evaporators, the refrigerant oil quantity in refrigerant circuit may be greater than the quantity which is found in the replacement compressor, if necessary add the remaining refrigerant oil quantity to the refrigerant circuit. Refer to → Chapter "Refrigerant Circuit, Flushing with Compressed Air and Nitrogen".

- Replace the dryer cartridge, receiver/dryer, or reservoir, and restrictor. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual).

- Examine the expansion valve for dirt or corrosion; replace if necessary. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual).

- Assemble, evacuate and charge the refrigerant circuit.


     Receiver/Dryer or Accumulator and Restrictor, Replacing after Cleaning Refrigerant Circuit

      Note Cleaning the refrigerant circuit means flushing it with refrigerant R134a. Refer to → Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant R134a" or blowing throu

     A/C Compressor Regulator Valve -N280-, Removing and Installing

      Note Certain functions on the A/C Compressor Regulator Valve -N280- (for example, a stuck valve or a disruption in the coil) can lead to a complaint regarding the A/C compressor (A/C syste

     Refrigerant R134a Capacities, Refrigerant Oil and Approved Refrigerant Oils

    Approved Refrigerant Oils and Capacities   Note As PAG (polyalkylene glycol) oil is highly hygroscopic (attracts water), opened containers are to be immediately resealed so as to be air-tigh


     Software update

    Introduction Applies to: vehicles with software update You can update your vehicle's software. The functions depend on the country and vehicle equipment: Update through the online system update Map material update for the navigation system Have the software update performed by an authorized Aud

     Luggage compartment lid

    General information WARNING Applies to: vehicles with anti-theft alarm system: When the vehicle is locked from the outside, no one, especially children, should remain in the vehicle, because the windows can no longer open from the inside. Locked doors make it more difficult for emergency work

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