SECTION 50 - CAB HEATING AND AIR CONDITIONING 31
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - High
High Pressure - Low
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - Normal
High Pressure - Normal
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - High
High Pressure - Normal
PROBLEM POSSIBLE CAUSE CORRECTION
Evaporator air not cold Internal leak in compressor (reed
valves, gasket, worn or scored pis-
ton rings or cylinder)
Discharge the system.
Replace the compressor.
Evacuate the system.
Charge the system.
Re-test.
PROBLEM POSSIBLE CAUSE CORRECTION
Insufficient cooling
Low pressure reading does
not fluctuate with changes in
temperature control switch
(pressure should lower until
compressor cycles)
Evaporator air not cold
System low on charge. Air or mois-
ture present in system
Perform leak test.
Discharge the system.
Repair leaks.
Replace receiver/drier.
Check oil level.
Evacuate the system.
Charge the system.
Re-test.
PROBLEM POSSIBLE CAUSE CORRECTION
Compressor cycles ON and
OFF too frequently
Defective temperature control (ther-
mostatic) switch
Stop engine and shut off A/C.
Replace temperature control switch.
Re-test system and check compres-
sor cycling.
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