Service valves

Fig 1: Service Valves

Courtesy of VOLVO CARS OF NORTH AMERICA.

The service valve for draining, vacuum pumping and filling with refrigerant
Service valve for draining and vacuum pumping.

One service valve is located on the low pressure side and one service valve is located on the high pressure side. The valves are different sizes. This is to avoid incorrect connection.

CAUTION:

Filling with refrigerant must only be carried out on the high-pressure side to prevent the risk of liquid refrigerant in the compressor.