Audi A4 Owners & Service Manuals

Audi A4: Service Station, Connecting with No Connection on Low- and High Pressure Side of Refrigerant Circuit

Audi A4 (B9) 2016-2024 Service Manual / Heating, Ventilation & Air Conditioning / A/C Service Station, Connecting / Service Station, Connecting with No Connection on Low- and High Pressure Side of Refrigerant Circuit

General Information

On the following vehicles, no service connection is provided for the service station on the low-pressure side of the refrigerant circuit; adapters must be used to connect the service station to the refrigerant circuit on these vehicles:

  • Audi 80, Audi Cabrio, Audi Coupe
  • Audi A4 up to 07.96
  • Audi 100/Audi A6 up to 03.97
  • Audi A8 up to 11.97


On vehicles with no or inaccessible connection at compressor, remove A/C Refrigerant Low Pressure Switch -F73- (bridge terminals in connector to A/C Refrigerant Low Pressure Switch -F73-) and screw adapter to this connection. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual).


  • The tools listed below are commercially available or can be obtained from local distributor or importer.
  • Should it be necessary to measure the pressures at the switch connections on the high-pressure side, use the adapter Adapter Set for Refrigerant Circuit -VAG1785/9- and proceed in the same manner.

Service Station, Connecting with A/C Adapter Set -VAG1786- to Refrigerant Circuit


A - Connection with valve (small valve insert) on low-pressure side of refrigerant circuit

B - A/C Adapter Set - Adapter 1 -VAG1786/1-.

C - Commercially available charging hose (short version with 5/8" thread on each end).

D - A/C Adapter Set - Adapter 2 -VAG1786/2- (for connection of quick-release coupling of service station -E-).


  • Assemble the adapter and charging hose as shown and connect to connection with valve -A- first.
  • The A/C Adapter Set - Adapter 2 -VAG1786/1- is only to be used at connections with "small" valve insert (standard for connection with valve for A/C Refrigerant Low Pressure Switch -F73- and gradually introduced as of 10.94 also at compressor).
  • Instead of the A/C Adapter Set - Adapter 1 -VAG1786/1-, the A/C Adapter Set - Adapter 10 -VAG1785/10- can also be used (remove valve from A/C Adapter Set - Adapter 10 -VAG1785/10 -or install valve opener in charging hose).

Service Station, Connecting with A/C Adapter Set - Adapter -VAG1785- to Refrigerant Circuit

- Remove the cap from the connection with valve -A- (at A/C compressor).

- Attach the O-ring -B- to the connection (8.9 mm; 1.8 mm).

- Screw the adapter VAG1785/10 -C- onto the connection -B-.

- Install the valve opener -D- with the appropriate seal in the charging hose connection.



  • The type of valve opener -D- and seals required depends on charging hose used (specific to manufacturer).
  • The quick-release coupling adapter is not required for connection on the low-pressure side of Audi vehicles.
  • Screw the charging hose -E- (to the service station) onto the A/C Adapter Set - Adapter 10 -VAG1785/10-.


To minimize the amount of air and moisture penetrating into the charging hoses and thus into the refrigerant circuit, the charging hoses should be connected together as illustrated.


A - Charging hose to service station

B - Hand shut-off valve

C - Charging hose (short version) with valve opener for connection to adapter -D-

D - A/C Adapter Set - Adapter 10 - VAG1785/10-

E - Charging hose (short version) with quick-release coupling adapter (for vehicles with quick-release coupling adapter on low-pressure side).

- Perform the planned tests and measurements.

Servicing Station, Connecting for Measuring and Testing

- Turn off the ignition.

- Connect the service station to the power supply.

- Assemble adapter set and screw to connection on low-pressure side.

- Connect the quick-release coupling adapter to the charging hoses of service station (handwheels not screwed in/hand shut-off valve not open).

- Switch on the service station and evacuate the charging hoses (only necessary if there is air in charging hoses).

- Switch off the service station.

- Remove the cap from the service connection/connection with valve (or remove low-pressure switch and bridge respective electrical connections).

- Connect the service station via the service connections with the quick-release coupling adapters to the vehicle refrigerant circuit.

- Install the handwheel on the quick-release coupling adapters only until valve is definitely open at refrigerant circuit connection (observe pressure gauge, do not strain valve).

- Perform the planned tests and measurements.


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