Case 580SR Service Manual page 790

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30
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - High
PROBLEM
Evaporator air warm
Liquid line hot (condenser out-
let to expansion valve tube)
High pressure switch cutting
out
Evaporator air not cold
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - Low
PROBLEM
Insufficient cooling
SECTION 50 - CAB HEATING AND AIR CONDITIONING
High Pressure - High
POSSIBLE CAUSE
Improper operation of condenser
Overcharged with refrigerant
Air in system
Expansion valve allowing too much
refrigerant to flow through the evapo-
rator
High Pressure - High
POSSIBLE CAUSE
Restriction in liquid line
CORRECTION
Inspect for dirty condenser restricting
air flow and cooling.
Check operation of condenser cooling
fans. Repair or replace as needed.
Check for overcharge as follows:
Stop the engine. Recover and recycle
the charge using correct recovery
equipment.
Recharge the system with the correct
quantity of refrigerant, replacing any
lost lubricant. Recheck performance
of air conditioning 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.
CORRECTION
Discharge the system.
Replace receiver/drier.
Inspect all lines and tubing from com-
pressor outlet to expansion valve.
Replace if needed.
Evacuate the system.
Charge the system.
Re-test.
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