A/C Charge Determination Test

Fig 13 Filter-Drier -- Typical:

The refrigerant system sight glass is a refrigerant level indicator. To check the refrigerant level, clean the sight glass and start the vehicle engine. Set the heater-A/C mode control switch to the Max (A/C) position, the blower motor switch in the High speed position, and the temperature control lever in the full left (Cool) position. The room temperature should be at least 21°C (70°F). After operating the system for a few minutes under these conditions, inspect the sight glass.

1. If the sight glass is clear, the compressor clutch is engaged, the compressor discharge line is warm, and the compressor inlet line is cool; the refrigerant system has a full charge.
2. If the sight glass is clear, the compressor clutch is engaged, and there is no temperature difference between the compressor inlet and discharge lines; the refrigerant system is empty or nearly empty. Connect a pressure gauge to the compressor discharge port. If the gauge reads less than 207 kPa (30 psi) the low pressure cut-off switch has failed.
3. If the sight glass is clear and the compressor clutch is disengaged; the clutch coil or the clutch control circuit is faulty Perform the low pressure cut-off switch test to determine if the clutch control circuit is open because of a low refrigerant system charge.
4. If the sight glass shows foam or bubbles, the system could be low on refrigerant. Some bubbles may appear in the sight glass on vehicles with the optional rear air conditioning, or when the room temperature is above 43°C (110°F), or below 21°C (70°F).
5. Set the engine speed to 1,300 rpm and set the blower motor switch in the High speed position. Block the air flow through the condenser to increase the compressor discharge pressure to 1,522 to 1,724 kPa (225 to 250 psi). If the sight glass still shows bubbles or foam, see the A/C Performance test procedure for further diagnosis.