A/C Charge Determination Test

Filter Drier Assembly - Typical:

The sight glass is a refrigerant level indicator. To check the refrigerant level, clean the sight glass and start the vehicle engine. Place the air conditioning controls on A/C, the blower switch on high and the temperature lever on cool. The room temperature should be at least 21°C (70°F). After operating for a few minutes in this manner, check the sight glass.
1. If the sight glass is clear, the A/C clutch is engaged, the compressor discharge line is warm and the compressor inlet line is cool; the system has a full charge.
2. If the sight glass is clear, the A/C clutch is engaged and there is no significant temperature difference between compressor inlet and discharge lines; the system is empty or nearly empty.
3. If the sight glass is clear and the A/C clutch is disengaged; the clutch is defective or, the clutch circuit is open, or the system is out of refrigerant. Check clutch circuit switches to determine condition. Also check the clutch coil for electrical continuity.
4. If the sight glass shows foam or bubbles, the system could be low on charge. Occasional foam or bubbles are normal when the room temperature is above 43°C (110°F) or below 21°C (70°F).

Adjust the engine speed to 1400 rpm. Block the airflow thru the condenser to increase the compressor discharge pressure to 1552 to 1724kPag (225 to 250 psig). If sight glass still shows bubbles or foam, system charge level is low.

The refrigerant system will not be low on charge unless there is a leak. Find and repair the leak