AC compressor stays on all the time – Common causes
If you have auto-climate control on, the AC compressor will run continuously, summer and winter, if the auto-climate control is on any setting other than off.
Low refrigerant level
If the amount of refrigerant in the AC compressor reservoir is reduced, most likely due to a leak in the coils, the compressor might not have enough refrigerant to effectively run the AC. Due to this inefficiency, the AC compressor will have to work harder than usual.
In this case, you’ll likely need a professional to find and repair the leak and restore the refrigerant to the correct level.
Leaks most commonly occur in worn O-rings, seals and hoses of the air conditioning system, followed by leaks in a pinhole of the condenser and evaporator, and leaks in the compressor shaft seal.
To detect leaks, add refrigerant to restore it to the correct level, then turn the AC on. The most simple but effective method is to spray soapy water to suspected areas and watch for bubbles.
If a leak occurs in the O-rings, seals or hoses, simply have them replaced will solve the problem. However, if the issue lies with a leaking condenser or evaporator or the compressor shaft seal, repair is expensive and more troublesome, which should be performed by a professional.
A condenser full of dirt and debris will not work as effectively as normal to cool down the compressed and hot refrigerant that passes through, resulting in the AC compressor having to overwork.
Dirty evaporator coil
Similar to the condenser, the evaporator coil may be covered with dirt and debris, impeding its drying process and the system’s overall cooling process, thus making the AC compressor work harder to cool your car’s interior.