- The sight glass is an indicator of the refrigerant level in the air conditioning system. To check the level, clean the glass and start the engine (Fig. 18.1). Press the air conditioner compressor on/off button, set the fan switch to the maximum speed position, and set the air temperature control knob to the maximum cooling position. After a few minutes of air conditioning operation in this mode, look through the sight glass.
Fig. 18.1. Location of the inspection window for checking the refrigerant level
1. If the sight glass is clear, the compressor electromagnetic clutch is engaged, the compressor discharge hose is warm and the inlet hose is cold, then the system is completely filled with refrigerant.
2. If the sight glass is clean, the electromagnetic clutch is engaged, but there is no significant temperature difference between the discharge and inlet hoses, which means that some of the refrigerant has escaped from the system.
3. If foam or bubbles are visible in the sight glass, this indicates that there is insufficient refrigerant. The system needs to be refilled with refrigerant.