A/C Charge Determination Test

Fig. 26 Filter drier assembly. Typical:

Check refrigerant level by cleaning sight glass on receiver drier unit, and starting engine. Set A/C control to A/C NORM blower switch to HIGH, and temperature lever to COOL. On vehicles equipped with semi-automatic temperature control, set control to A/C NORM or Bi-Level, blower switch to HIGH, and temperature lever to 65°F.
Roll down windows so passenger compartment temperature remains above 65°F. Ambient temperatures should be above 70°F. After a few minutes of operation, check sight glass.
1. System has full charge if sight glass is clear, compressor clutch is engaged, compressor discharge line is warm and compressor inlet line is cool.
2. System is nearly empty if sight glass is clear, clutch is engaged and no significant difference in temperature is noted between compressor inlet and discharge lines. If compressor runs continuously on models with 4 cylinder engines, anti-diesel relay may be defective. Connect gauge to compressor discharge port. If gauge indicates less than 25 PSIG, low pressure cut-out switch has failed.
3. If sight glass is clear and clutch is disengaged, clutch is defective, clutch circuit is open or system is out of refrigerant. Perform Low-pressure cut-off switch test as described under "Low Pressure Cut-Out Switch Test." Check cycling clutch switch (if so equipped), and clutch coil for continuity.
4. If sight glass shows bubbles, system could be low on charge. Occasional foam or bubbles are normal when ambient temperature is above 110°F, or below 70°F. Adjust engine speed to 1300 RPM on all eight-cylinder cars. Block air flow through condenser to increase compressor discharge pressure to 225-250 PSIG. If bubbles are still observed in sight glass, system charge level is low due to leakage. If leak can be repaired without discharging system, low refrigerant level can be repaired as follows: Maintain discharge pressure at 225-250 PSIG and add refrigerant gas through compressor line until foam is cleared from sight glass. When foam has cleared, add an additional 14 ounces of refrigerant.