Why Does My Car AC Compressor Turn On And Off?

It is common for a car’s engine to operate the compressor to keep the inside pressure from reaching specific maximum levels. If the car’s compressor is not frequently cycling on and off, everything is fine. 

But if the switch between on and off is too frequent, you have got something to worry about. But let’s not jump to a conclusion. First, you have to find the answer: why does my car AC compressor turn on and off?

The reason behind your compressor turning on and off can be as simple as your car evaporator being extremely cold. Or it can be related to an inadequate supply of electricity, lack of refrigerant, low pressure inside the system, or a mechanical fault inside the compressor.

Ensure that your concern is justified. First, we’ll take a look at what the frequency of switching should be. Then look for all the possible reasons.

Let’s look at all these details.

What Is A Normal AC Compressor On And Off-Cycle?

The car’s AC compressor goes on and off quickly, and the short-cycling process is absolutely normal. But if it keeps doing it more frequently or it is working non-stop, it should be a concern. So, it is really important for us to know the normal cycling duration of a normal AC compressor.

The AC cycle means the amount of time the compressor is working to keep your car’s internal environment cold. A normal AC compressor should have three to four cycles per hour, each cycle lasting for about 15-20 minutes. It also depends on the temperature. 

If the internal environment has a higher temperature, expect each cycle to last longer than usual. So, if it exceeds the normal range, you should bring your car to a technician.  

4 Reasons Why The AC Compressor Keeps Turning On and Off

There can be a wide range of reasons behind a faulty compressor which keeps turning on and off frequently. Some of these need an expert hand to repair, and some only need caution.

Here are 4 common reasons:

1. Pressure Cutout

There are some pressure sensors inside the compressor. When there’s an inadequate supply of refrigerant, the systemic pressure falls below the threshold level, and the low pressure forces the system to shut down to prevent damage to the engine.

The pressure is over the threshold level in a non-running system. It allows the system to turn on the compressor. As it starts, the pressure starts to fall. When the lower pressure limit goes below the threshold level, the system forces the compressor off. So, any fluctuation other than the normal cycle would cause the compressor to turn on and off frequently.

2. Evaporator Being Extremely Cold

The automobile has multiple thermostats, one along the coil to ensure that it is not supercooled. Another that controls the main compressor power to turn on and off as required to provide the necessary cooling. 

This is not related to the fan speed, which is responsible for passing car air towards the evaporator to chill it. Till the car’s evaporator is cold, this would keep delivering cold air into the car, and as a result, the compressor cycle would keep turning on and off.

Usually, your car’s air conditioner has far more conditioning capability than is required. If you’re in a heated car and wish to cool it off fast, it consumes its maximum capacity. If left on full power, the evaporator coils may freeze, and even if they do not, the inside may be extremely chilly and unpleasant. And when the evaporator is cold, the compressor will turn on and off.

3. Debris In The Evaporator 

If debris has made a home in your evaporating coil, it will affect the drying process, which will, in turn, create obstacles in maintaining a cool car atmosphere. So, the system will have a hard time cooling down your car’s temperature. Then the compressor will have to do much more work on it, which might lead to your AC compressor switching between on and off.

4. Refrigerant Issues

There are two types of refrigerant issues that can occur in your car that can lead to an AC compressor turning on and off. One is having a scarcity of refrigerant, and another is dirt accumulating in the condenser. Both affect the compressor in similar ways.

A. Lack of refrigerant

When your car’s AC compressor is low on the refrigerant, the compressor can frequently turn on and off. But this can create more problems when your system is undercharged.

An R-134a refrigerator tends to blow much cooler air when your system is lacking refrigerant. However, the scarcity of refrigerant implies a lesser amount of oil is flowing through the system. This deficiency could cause your AC compressor to fail completely. In this case, you might have to replace the whole system because it is nearly impossible to fix the system then. 

A variety of factors might produce the low level. It could be due to a leak within the coil. This can fade by itself. Consult an expert who can address this problem. They must locate and repair the leak, then restore the refrigerant so that your AC compressor can function properly.

B. Dirty Condenser

When the condenser is extremely dirty, the refrigerant does not work properly, which leads to the compressor switching on and off. Also, the same issue of lack of oil supply flow occurs. And as we learned, that leads to permanent damage or failure, which can be fixed by just taking the debris out

Conclusion

Why does my car AC compressor turn on and off? Well, it can be for various reasons. However, if the compressor stays on for about 45 seconds or more, and only switches on briefly before turning off, then it’s nothing to worry about.

But if the transition of turning on and off is too rapid, you should take your AC compressor for repair. They will check it for any possible leaks. You will also know if your compressor is just low on refrigerant. Your problem will easily be fixed.