Troubleshoot Air Conditioning

Troubleshoot Air Conditioning

by Larry Carley copyright 2019 AA1Car.com

A/C COOLING PROBLEM?

The most likely cause of an automotive air conditioner cooling problem is no refrigerant in the system. If the refrigerant has escaped past a leaky compressor or O-ring seal, leaked out of a pinhole in the evaporator or condenser, or seeped out through a leaky hose, the leak needs to be identified and repaired before the system is recharged.

On many systems, the compressor will not turn on if the refrigerant is low because the "low pressure safety switch" prevents the compressor clutch from engaging if system pressure is low. This protects the compressor from possible damage caused by a lack of lubrication.

One of the first things you should check, therefore, is compressor engagement. If the compressors magnetic clutch is not engaging when the A/C is turned on, the problem may be a blown fuse or a wiring problem. If the fuse is blown, replacing it may restore cooling temporarily. But the underlying reason for the fuse blowing in the first place needs to be identified and corrected to prevent the same thing from happening again.

If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch is defective and needs to be replaced. If there is any evidence of leakage around the compressor shaft seal, the seal should also be replaced.

If the clutch works but fails to turn the compressor (the belt may squeal in protest!), the compressor has seized and needs to be replaced.

Cooling Problems with Variable Displacement Compressors

On some late model vehicles, the A/C compressor does not have a clutch to cycle it on and off. The compressor runs all the time when the engine is running, and it uses Variable Displacement to increase or decrease the volume of refrigerant it pumps through the system.

With this type of setup, the climate control module or PCM monitors the temperature inside the vehicle and changes the displacement of the compressor as needed to increase or decrease cooling. Inside the variable displacement compressor is a swash plate that changes the stroke of the pistons as they move back and forth. Increasing the stroke increases the volume of refrigerant pumped through the system for more cooling. Decreasing the stroke reduces the volume of refrigerant pumped through the system to reduce cooling.