Car AC Compressor Turns On and Off Frequently / Randomly?

Updated: | Author: Steve Freling | Affiliate links may be present.

Cool air conditioning in your car on a hot day feels great! It is not so great, however, when the air conditioning isn’t working properly.

The AC compressor compresses the refrigerant in the air conditioner in order to blow cool air into your car. If the compressor is turning on and off frequently or randomly, it is usually a sign that there is a malfunction.

It is normal for the car air conditioning compressor to turn off and on at regular intervals. However, if it turns off and on frequently or randomly, it may indicate that there is a problem. The coolant could be low due to a leak, there may be coolant stuck in the line, there may be a blown fuse, malfunctioning blower, or faulty relay. Or, it could be that the entire compressor needs to be replaced.

What are the Signs that My Car Air Conditioning is Malfunctioning?

Here are a few things that may point to a problem with the AC compressor. Normally, an air compressor lets out a low hum. If there is a problem, you may hear clicking, banging, squealing, or buzzing.

The Car AC Compressor is Short Cycling

Airflow to the air conditioner will stop if the intake vents are blocked. Without a warm air supply, the thermostat will switch off the compressor. This will cause the compressor to short cycle.

The Car AC Compressor Shuts Off After a Few Seconds

If the compressor turns on, then turns off after a few seconds, that could also indicate that something is malfunctioning within the air conditioning system. Overheating can stress the air conditioner, and cause it to turn off.

The Car AC Turns On and Off Randomly

It is normal for the compressor to turn on and off while the air conditioner is running. However, if the air conditioner is working infrequently, and not cooling consistently, it is due to a problem with the system, such as low coolant, or a frozen condenser.

Why is the Compressor Turning On and Off?

If your air conditioner is short cycling or turning on and off frequently, it is most likely due to one of the following causes.

Low Coolant

If there is not enough freon in the air conditioner, the system overheats and turns off. Low coolant could be due to a freon leak, or a faulty expansion valve. Take your vehicle to the mechanic to get the air conditioner recharged and any potential leaks fixed.

Too Much Coolant in the Line

Sometimes there will be excess freon in the line after the air conditioner is recharged or the vehicle is serviced. This will cause the compressor to turn on and off, but it should work itself out over time.

Malfunctioning Blower

A faulty blower motor could cause the compressor to turn on and off. Typically, you’ll hear the blower running continuously, which will drain the car battery.

Faulty Relay

The relay is a part of the car’s electrical system that converts electrical stimuli into larger currents. A bad relay could limit the amount of electrical current that travels to the AC compressor, causing it to turn off and on.

Blown Fuse

A blown or faulty fuse will cause your car’s air conditioner to switch off and on. The solution is as simple as changing the fuse.

Bad Compressor

Unfortunately, sometimes air conditioning compressors go out. You may notice that the air coming out of the vents is cool, but not cold.

Also, there may be noises from the compressor. The bearings in the compressor may lose lubrication or wear out. This will cause the compressor to make squealing or grinding noises. Though these parts may sometimes be repaired, often it is better to replace the compressor entirely, even though it is a more pricey repair.

How Can I Fix the AC Compressor?

Take It to a Mechanic

It is illegal to release freon into the environment. Therefore, most repairs on an air conditioning system are not possible in a home garage. The mechanic has a special collection receptacle to catch the released coolant.

Also, there are air conditioning recharge kits available, however, there is no way to determine how much charge there is in the air conditioner, or how much you are adding. You can overcharge the system, and cause damage.

DIY Repair

There are a few air conditioning repairs that can be made in a home garage. First, you can check the wires to see if the compressor is connected properly.

You can also clean the condenser coils. Grease and grime build up on the coils over time. Use a condenser coil cleaner to permeate the grease, then rinse clean.

Final Thoughts

There are a number of possible causes for an AC compressor to turn on and off randomly. Pinpoint the issue with your car’s air conditioning compressor, get it repaired, and be driving cool once more! Happy driving!

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About Steve Freling

Steve has worked for more than 20 years as an automotive mechanic, and later run his own repair shop for both cars and motorcycles. He's a maintenance freak, and generally pretty good at troubleshooting!

3 thoughts on “Car AC Compressor Turns On and Off Frequently / Randomly?”

  1. 2014 Nissan Sentra…ac trying to come on but goes off in seconds. If car is at idle it almost dies when compressor tries to come on. Pressure switch ??


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