A/C Charge Determination Test

The sight glass is a refrigerant level indicator. To check the refrigerant level, clean the sight glass and start the engine. Push the A/C button to operate the compressor, place the blower switch to high and move the temperature control dial to max cool. After operating for a few minutes in this manner, check the sight glass.
1. If the sight glass is clear, the magnetic clutch is engaged, the compressor discharge line is warm and the compressor suction line is cool; the system has a full charge.
2. If the sight glass is clear, the magnetic clutch is engaged and there is no significant temperature difference between compressor suction and discharge lines; the system has most of its refrigerant charge.
3. If the sight glass shows Than or bubbles, the system could below on refrigerant or the receiver drier is restricted. The system has to be tested, leak checked then recharged with refrigerant.