SECTION 50 - CAB HEATING AND AIR CONDITIONING 29
PERFORMANCE TEST DIAGNOSIS
Pressure gauge values: Low pressure - Low
High Pressure - Low
PROBLEM POSSIBLE CAUSE CORRECTION
Evaporator air not cold Low refrigerant charge Perform leak tests and repair.
Evacuate the system.
Charge system, re-test system.
Evaporator air warm Extremely low refrigerant charge Perform leak tests and repair.
Evacuate the system.
Charge system, re-test system.
Evaporator air cool but not
sufficiently cold
Low pressure switch cutting
out
Expansion valve to evaporator
tube shows considerable con-
densation or frost
Too cold to touch
Expansion valve not permitting suffi-
cient flow
Stuck valve
Check expansion valve as follows:
Set for maximum cooling.
Low pressure gauge should lower
slowly.
If expansion valve is defective:
Discharge the system.
Replace the expansion valve.
Evacuate the system.
Charge the system.
Re-test.
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