A/C Charge Determination Test

Fig 5 Filter Drier And Sight Glass:

The filter-drier is equipped with a sight glass that is used as a refrigerant level indicator only. This sight glass is not to be used for A/C performance testing. To check the refrigerant level, clean the sight glass. Then start and warm up engine, and hold idle at 1,100 rpm.

Place the air conditioning control on A/C and high blower. The work area temperature should be at least 21°C (7O°F).
- If the compressor does not engage, the refrigerant level is probably too low for the Dual Pressure Cut-Off switch to detect.
- If compressor clutch does not engage, refer to Testing Refrigerant System for Leaks.
- If compressor clutch engages, allow approximately one minute for refrigerant to stabilize. View refrigerant through sight glass. The suction line should be cold to the touch and the sight glass should be clear.

If foam or bubbles are visible in sight glass, the refrigerant level is probably low.
- Occasional bubbles are normal when the temperature is above 43°C (11O°F) or below 21°C (70°F).

If suction line is cold and occasional bubbles are visible in the sight glass, block the condenser air flow.
- This will increase the compressor discharge pressure (Do not allow engine to overheat).
- Bubbles should dissipate. If not, the refrigerant level is low.

CAUTION: The filter-drier used in a R-134a refrigerant system will not interchange with a filter/drier from a R-12 refrigerant system.