System Operation Check

The individual components of the refrigerant system will often give clear signs of their malfunctioning. Use the following general descriptions to pinpoint faulty components:

BLOWER
If inoperative, examine switches, fuses, connections, wiring and the blower motor. If blower is operating but the air output is low, check for loose wire connections or shorts, undercharged battery, dirty or loose switch contacts, or a faulty blower motor. For more detail,Symptom Related Diagnostic Procedures

AIR DISTRIBUTION
Inspect the air distribution system for obstructions and ensure proper door operation.

If the blower is circulating the air but there is no cooling, check:
COMPRESSOR DRIVE BELT
Ensure it is not broken or slipping. If the pulley is turning but the compressor shaft is not, check the magnetic clutch.

COMPRESSOR
A faulty compressor will display one or more of the following symptoms: noise, seizure, leakage or low inlet and discharge pressure. A steady, resonant noise from the compressor is not necessarily an indication of a problem, but irregular metallic rattling may indicate broken parts and should be investigated. A thumping noise from the compressor and a cool, sweating suction line into it may indicate an overcharged system. Check seizure by disengaging the magnetic clutch and rotating the driven plate. If the compressor is seized, the driven plate will not rotate.

False compressor seizure may occur after an extended period of disuse or storage. Lubricating oil drains away from the polished surfaces of ball seats and axial plate and the compressor appears to be seized. Use a clutch hub holding tool to turn the compressor in the opposite direction of rotation at least three revolutions. Check for false compressor seizure if compressor has not been used in a month or longer.

If compressor is not seized but will not rotate, check for current at magnetic coil. Low discharge pressure may be caused by faulty seals within the compressor, a restriction in the compressor or elsewhere, or by a low refrigerant charge. The compressor must have the correct amount of the proper viscosity oil. Excess oil will restrict refrigerant circulation and reduce compressor outlet pressure. Fore more detail,Symptom Related Diagnostic Procedures

CONDENSER
The condenser may malfunction either due to leakage or restriction. If restricted, compressor discharge pressure will be excessive. Icy or frosty spots on the condenser will indicate a partial restriction within the condenser. Ensure all foreign matter is removed from the front of the condenser. Similarly, bent cooling fins will block air flow through the condenser and result in high discharge pressure. For more detail,Symptom Related Diagnostic Procedures
EVAPORATOR
A faulty evaporator will provide insufficient cooling to the vehicle. The core may be restricted with dirt, the case may be cracked, or a seal may be leaking sufficiently to prevent cooling. If evaporator restriction is due to icing, the expansion valve, capillary tube or suction throttling valve, if equipped, may be at fault and should be investigated.Since there is a constant condensation of atmospheric moisture on the outside of the evaporator coils, ensure that the draining system is unobstructed and clean.

NOTE: Some vehicles have an auxiliary evaporator in the trunk or between the headliner and the roof.

For more detail, Symptom Related Diagnostic Procedures

REFRIGERANT LINE RESTRICTIONS
1. A restricted suction line is indicated by low suction pressure at the compressor, low discharge pressure and little or no cooling.
2. A restricted discharge line will usually cause the pressure relief valve to open.
3. A restricted liquid line will cause low suction and discharge pressures and little or no cooling.