Case 580SR+ - Page 790

30 SECTION 50 - CAB HEATING AND AIR CONDITIONING
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - High
High Pressure - High
PERFORMANCE TEST DIAGNOSIS CHART
Pressure gauge values: Low pressure - Low
High Pressure - High
PROBLEM POSSIBLE CAUSE CORRECTION
Evaporator air warm
Liquid line hot (condenser out-
let to expansion valve tube)
High pressure switch cutting
out
Improper operation of condenser
Overcharged with refrigerant
Air in system
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.
Evaporator air not cold Expansion valve allowing too much
refrigerant to flow through the evapo-
rator
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.
PROBLEM POSSIBLE CAUSE CORRECTION
Insufficient cooling Restriction in liquid line 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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