What Causes AC Compressor to Lock Up

What Causes AC Compressor to Lock Up

Have you ever experienced the frustration of your air conditioner blowing hot air instead of cool relief during the summer? I also faced this problem last summer. So, what causes AC compressor to lock up?

The AC compressor can lock up due to lack of lubrication, overheating, electrical issues, contaminants and debris, mechanical failure, and clogged refrigerant lines.

After deep research, I was able to find reasons why AC compressors lock up, and finally, I repaired the AC compressor myself. In this blog post, I will explain what causes AC compressor to lock up and how I diagnosed and fixed the compressor.

What Causes AC Compressor to Lock Up?

AC compressor of car

Let’s move on to the topic: what causes AC compressors to lock up?

Here are the things I found in my research that cause the AC compressor to lock up.

Lack of Lubrication

The AC compressor needs oil to lubricate it and reduce friction. So, what happens if there is low oil or the remaining oil is contaminated? It leads to increased friction and causes the AC compressor to seize.


The second main reason is excessive heat. When the compressor runs for an extended period of time, especially in hot weather, it will overheat. This causes the seizure of internal compounds and results in a locked-up AC compressor.

Electrical Issues

wiring of a car

Faulty clutch coils or wiring are the main culprits here. If the clutch fails to engage properly or to not disengage it can result in the compressor seizing.

Contaminants and Debris

Foreign particles such as dirt and debris, as well as metal fragments, disturb the free movement of the compressor. Long-term accumulation of debris results in a locked-up compressor.

Mechanical Failure

Components within the compressor, such as pistons, valves, or bearings, can wear out over time. This is another reason for the compressor to seize. This happens due to the aging of the compressor.

Clogged Refrigerant Lines

Final reason. If the refrigerant hoses are blocked, the compressor has to put in extra effort. With time, this also causes the compressor to lock up.

How To Prevent AC Compressor Lockups in The Future?

Now you know what causes AC compressor to lock up. Then how can we prevent that?

Preventive MeasuresDescription
Clean or Replace Air FiltersRegularly clean or replace air filters to improve airflow and reduce strain on the compressor.
Maintain Proper Refrigerant LevelsCheck refrigerant levels regularly to ensure they are at the recommended levels.
Check for Refrigerant LeaksRepair them as soon as possible to prevent compressor damage.
Keep the Condenser CleanClean the condenser unit regularly and ensure proper airflow
Address Electrical IssuesPromptly address any electrical problems like faulty wiring, loose connections, or worn-out components.
Avoid Overworking the AC SystemSet reasonable temperature settings, avoid continuous operation, and give the system occasional breaks to prevent overheating.
Schedule Regular MaintenanceRegular inspections, cleaning, and servicing by a professional technician to identify and fix minor issues
Seek Professional HelpContact a professional HVAC technician if you notice any unusual noises, vibrations, or performance issues with your AC system.

How To Fix a Locked-Up AC Compressor?

This is how I fixed my locked-up AC compressor.

First, I gathered the necessary tools.

Tools needed:

  • Wrenches
  • Pliers
  • Screwdrivers
  • Safety goggles
  • Gloves
  • Clean rag

I parked my car in the garage, turned off the engine, waited a few minutes for the engine to cool down, and wore safety gloves and goggles.

Then I disconnected the battery by removing the negative battery terminal.

Next, I located the AC compressor. It was located at the front of the engine, and its pulley was connected to the serpentine belt. It meant I needed to remove the serpentine belt first.

So, I loosed the belt tensioner pulley to loosen the serpentine belt and slide the belt of the AC compressor pulley.

Then I loosened the nuts that secured the AC compressor to the bracket and disconnected the wires connected to the compressor. Next, I got the compressor out of the engine bay and put it on the floor for better access.

I tried to rotate the AC compressor clutch by hand. It was so tight that it didn’t rotate anymore.

I removed the clutch and the pulley by removing the bolts from the compressor.

I looked in the compressor to find the reason behind the lockup. I was able to identify a damaged bearing as the reason. So, I removed and replaced the faulty bearing with a new one.

Then I cleaned the clutch pulley and the surrounding area to remove the debris and contaminants. I also applied some lubricants to the moving parts of the clutch assembly.

Next, I reinstalled the clutch and the pulley and fixed the AC compressor to the car.

Finally, I reinstalled the serpentine belt on the AC compressor pulley and ensured proper engagement by tightening the tensioner pulley.

After connecting the battery terminal, I turned on the AC and waited some time to check whether there were any abnormal sounds. No problems. The AC compressor rotated freely. As before, cold air also came from the vents.

If you feel my method is too hard, you can also bypass the AC compressor with a serpentine belt.


Can you spin the AC compressor by hand?

Yes, the air conditioner compressor clutch on a car should typically be able to be turned by hand. You may need to exert some slight effort to get it to spin around; it won’t spin at the slightest touch, but it should spin anyway.

How does an AC compressor affect the car?

In order to supply your automobile with cool, comfortable air, the compressor pumps refrigerant through the air conditioning system. Your car won’t be able to cool the air it circulates inside your cabin without refrigerant circulation.

Will the car AC compressor work without gas?

The use of refrigerant gas is necessary to cool warm air down. Parts of the refrigerant are lost via the system as it changes from a gas to a liquid over time, which means there is less of it available to help cool the warm air.

Which gas is used in the AC compressor?

A refrigerant used in air conditioning systems is freon, a non-combustible gas. To help create cool air that can be cycled throughout your AC system, this freon goes through an ongoing evaporation process.


I hope you understand what causes AC compressor to lock up and how to prevent it. Regular maintenance is crucial to preventing AC compressor issues. Have a nice day!

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