Case 580SR Service Manual page 789

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PERFORMANCE TEST DIAGNOSIS
Pressure gauge values: Low pressure - Low
Evaporator air not cold
Evaporator air warm
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
SECTION 50 - CAB HEATING AND AIR CONDITIONING
High Pressure - Low
PROBLEM
Low refrigerant charge
Extremely low refrigerant charge
Expansion valve not permitting suffi-
cient flow
Stuck valve
POSSIBLE CAUSE
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CORRECTION
Perform leak tests and repair.
Evacuate the system.
Charge system, re-test system.
Perform leak tests and repair.
Evacuate the system.
Charge system, re-test system.
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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