System Performance Test - Temp & Pressure Relationships

1. Park vehicle indoors or in a spot shaded from direct sunlight and sheltered from prevailing winds.
2. Connect a suitable gauge manifold to low and high side service valves.
3. Place dry and wet bulb sensors, suitable to measure air temperature and relative humidity, at recirculation air intake and 3.3 ft. in front of condenser.

NOTE: Sensors must be shaded from direct sunlight.

4. Place a suitable temperature sensor in center A/C outlet.
5. Open all windows fully, close doors and hatch, and open hood.
6. Start engine and set to run at 1500 RPM.
7. Place A/C control in maximum cooling position, blower on high speed, and air control in recirculation position.
8. Observe compressor clutch. If clutch fails to engage, refer to compressor clutch and compressor diagnosis charts in "SYSTEM DIAGNOSIS".

Fig. 32 Sight glass inspection diagnosis chart:

9. After 5 minutes of operation, perform sight glass inspection, Fig.32:
a. Bubbles seen in sight glass are affected by ambient temperature. At temperatures below 68 deg. F., bubbles are less likely to show than at temperatures above 68 deg. F.

NOTE: Always charge system with specified amount of refrigerant. Do not over-charge.

b. If receiver/drier screen is clogged, bubbles will appear even when system is fully charged.
10. After 10 minutes of operation, note temperature and humidity readings and system pressures:
a. When ambient temperature is low, air discharge temperatures will be lower.
b. When blower speed and/or relative humidity are low, discharge (high side) pressures will be lower than normal.

Fig. 34 A/C system performance specifications:

Fig. 34 A/C system performance specifications:

11. Compare test readings with system performance specifications, Fig. 34, noting the following:



a. If evaporator discharge temperature is not within specifications, refer to "INSUFFICIENT COOLING."



b. If system pressures are not within specifications, refer to "REFRIGERATION SYSTEM DIAGNOSIS."