Auto A/C Expansion Valve Troubleshooting

Written by andrea stein
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Auto A/C Expansion Valve Troubleshooting
Auto air conditioning (AC) expansion valves can experience problems that require troubleshooting. (luxury car - model toy car image by alma_sacra from

In an auto compressor, liquid refrigerant under high pressure circulates to the auto air conditioning (AC) expansion valve, which removes pressure from the refrigerant to allow it to expand and convert to a vapour. Auto AC expansion valves can fail or malfunction for numerous reasons. Troubleshooting can resolve most of these issues.

Low Suction Pressure

Debris from deteriorating old hoses or sludge from moisture-contamination can travel in the refrigerant to the AC expansion valve and cause blockage, resulting in low suction pressure. Replacing the contaminated receiver-dryer, the container which stores refrigerant from the condenser, typically restores proper function.

High Suction Pressure

AC expansion valves can become loose or stick open, typically indicated by higher than normal high side pressure, or pressure on the output side of the compressor. Tighten the loose AC expansion valve or replace it as needed.

Evaporator Won't Cool

A frozen or defective AC expansion valve can cause the evaporator, the device which converts liquid refrigerant into vapour, to not cool properly. Replacing the defective valve, or evacuating and replacing the receiver-dryer, typically restores evaporator function.

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