The hottest days of summer are over, yet you notice that your car’s air conditioner is running all the time or constantly turning on and off. If it’s not due to the weather, the air conditioning compressor stays on all the time, which means there is a problem with the unit.
If the issue is not resolved as quickly as possible, you will face a staggering electricity bill, and your air conditioner will undergo additional wear and tear due to unnecessary overworking.
It should be noted that the compressor has the second highest failure rate among all components of the air conditioning system. Discover the possible reasons why AC compressors stay on permanently and how to fix this common maintenance issue.
What is the purpose of an AC compressor?
The compressor is the component that powers the air conditioning unit.
When you turn on the air conditioner, the compressor compresses and heats the refrigerant, a special fluid mixture. This compressed and hot refrigerant is then sent through the condenser to cool down.
The refrigerant then passes through the dryer to remove contaminants. Once purified, the compressed refrigerant goes through the expansion valve, where it is relieved of its pressure. After passing through the evaporator, the refrigerant is now super clean, dry, and cold.
To create the bursts of cold air coming from your car’s air conditioner, air is sent through this newly cold refrigerant in the compressor tank to cool down, then blown through the fans.
Why does an AC compressor turn on and off?
It is normal for your car’s air conditioning compressor to turn on and off. For example, on the hottest days, the more you set your air conditioning to a cool level, the more the compressor has to work to maintain the desired temperature.
Once the desired temperature is reached, the air conditioning compressor may stop for a while until there is a change in your car’s temperature. Thus, the air conditioning system turning on and off is not a problem, but the frequency of the cycles can indicate issues.
An example of such abnormal cycling frequency is that instead of turning on and off, the AC compressor stays on all the time.
AC compressor stays on all the time – Common causes
Automatic temperature control
If automatic air conditioning is enabled, the air conditioning compressor will run continuously, summer and winter, if the automatic air conditioning is on a setting other than off.
Low refrigerant level
If the amount of refrigerant in the air conditioning compressor tank is reduced, probably due to a leak in the coils, the compressor might not have enough refrigerant to operate the air conditioning effectively. Due to this inefficiency, the AC compressor will have to work harder than usual.
In this case, you will likely need a professional to find and repair the leak and restore the correct refrigerant level.
Leak detection
Leaks most often occur at the O-rings, seals, and worn pipes 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 on the air conditioner. The simplest but most effective method is to spray soapy water on the suspected areas and watch for bubbles.
If a leak occurs at the O-rings, seals, or pipes, simply replacing them will solve the problem. However, if the issue is from a leak in the condenser or evaporator or the compressor shaft seal, the repair is costly and more tedious and should be done by a professional.
Dirty or clogged condenser
A condenser filled with dirt and debris will not work as effectively as usual to cool the compressed and hot refrigerant passing through it, forcing the air conditioning compressor to overload.
Dirty evaporator coil
Similar to the condenser, the evaporator coil can be covered with dirt and debris, hindering its drying process and the overall cooling process of the system, thus forcing the air conditioning compressor to work harder to cool the inside of your car.
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How much to replace an AC compressor?
If you are experiencing issues with your air conditioning compressor without knowing the exact reason, it is best to have it repaired. Only EPA-certified mechanics can service mobile air conditioning systems.
You might be wondering how much it costs to replace an air conditioning compressor. The average cost for replacing an air conditioning compressor is between $500 and $700 depending on the car in question. Labor costs alone are estimated at just over $200.
Rest assured, an air conditioning compressor typically lasts 8 to 10 years, which generally corresponds to the length of time an average car owner would keep their car.