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What You Should Do if Your AC Clutch is Not Engaging

AC Clutch not Engaging

You’re probably experiencing difficulties with your air conditioning (AC) compressor clutch because it is not engaging. If so, then you’ve come to the right place. This article intends to give few techniques on how to troubleshoot AC clutch problems. It also gives an insight into how the system works.

Read on and learn how to diagnose and fix AC compressor clutch issues.

AC clutch not engaging? Do this quick check to know why

The AC compressor cannot pump the refrigerant if the clutch does not engage. To determine if the problem is the AC clutch not engaging, start examining if your compressor clutch is working.

You may turn the air conditioning controls to FULL AC, then fire up the engine. Check the front of the compressor clutch. If the pulley and the clutch are both spinning it shows that the clutch is engaged with the pulley correctly. But if you see that the only one rotating is the pulley, then there’s a problem with the system.

What is the AC clutch and how does it work?

The AC compressor is empowered by the flywheel of a car’s engine. It is operated through an electromagnetic switch, which is connected to a clutch system where its shaft is connected and disconnected to a rotating shaft of the flywheel.

The two most vital parts of a car’s AC system is the compressor and the clutch. Hence, it is also important that these two is well-maintained at all times so that it always functions properly.

Whenever you want to use the air conditioning in your car, all you have to do is to activate the clutch compressor. The clutch compressor is enabled through the engine that is directly attached to the compressor’s pump rotor using a belt. However, most car AC systems now use an electromagnetic clutch piece that engages the compressor to spin the air conditioning unit.

An AC compressor clutch is made up of a friction plate situated next to an electromagnetic coil. Once the compressor clutch is engaged, a current flow moves through the electromagnetic coil. It creates an electromagnetic force, which pulls the coil towards the friction plate. This gives power to the pump rotor that keeps the compressor running.

How to check whether your AC clutch is working

Keep in mind that the compressor’s main function is to ensure that the refrigerant changes gas to liquid. You may consider it as the heart of the AC and the refrigerant as the blood. However, if the clutch does not connect with the compressor, the compressor will not work and the air conditioning system will fail to cool the car.

Try checking if the clutch is in good condition by applying these steps:

  • Turn the AC controls to maximum air conditioning.
  • Start the car engine.
  • Look closely and observe the front part of your clutch.
  • Make sure that the clutch and the pulley is spinning simultaneously.
  • If the only rotating part is the pulley, then the clutch fails to run.

Here is a useful tip: If you’re not confident to do the examination yourself, it is best to work with a car expert. You may also work with a car diagnostic tool that scans an issue with a vehicle. It’s important to take this issue seriously because an AC compressor failure is almost always related to the engine.

Common reasons why the AC clutch doesn’t engage

There are many reasons why an AC clutch does not engage. It could be because of a blown fuse, a bad clutch coil, or an open on the wire to the clutch coil. It could also be of poor ground or a low-pressure lockout.

There are many ways for AC compressor clutches to receive power. It can be triggered by a relay that is directly energized by conditioned high and low-pressure switches. Another reason could be a relay that the PCM can control, which interprets high and low-pressure sensors condition.

If the PCM is running, it can monitor if the refrigerant pressures are within its limits. Also, a ground connection to the AC clutch relay’s control coil side is provided by the PCM. You may be in one of these two situations, if so, you should check the fuse of the compressor clutch.

Clutch sensor- default lockout

Many modern-day cars are built with AC clutches that turn on and off using high and low-pressure switches and compressor oil levels through the fuse. There are three reasons why the compressor clutch does not engage, especially if the sensor detects them. These include low or excess refrigerant and insufficient oil.

Burnt fuse

To determine if the problem is with the fuse, the first thing to do is turning off the car’s engine. Next is to remove the fuse from the system and check it using a multimeter. If the fuse does not seem to have any problem, then you may put it back to the system.

Clogged condenser

Tiny bits of metal can clog your AC condenser. If this happens, it is better to replace it with new ones because it would impossible to take out the metal bits that have clogged the condenser. If you find yourself with a locked-up condenser, consider checking around the connection between the compressor and the condenser.

Broken receiver/ drier

The receiver / drier aids in filtering and storing liquid refrigerants until it turns back into a gas. You can also examine this for noise and smell issues. If it is not working properly, consider replacing it with a new one.  

Leaking evaporator coil

The evaporator coil is found inside your car’s cabin. This car AC element helps blow the air to cool it down. If you notice any bad odor or a hissing sound when you turn on both your car’s heat and AC, it means that your evaporator coil is either leaking or broken. This may require fixing or replacement. However, this piece may cost you too much to replace.

Broken AC expansion valve

Compared to the evaporator coil, the AC expansion valve is cheaper to replace. It is also a simple replacement to do. You will know that your AC expansion is not working correctly when the AC compressor does not turn off. It may be because the vents are covered with frost. Consequently, the vents may be giving off heat.

Other reasons

  • Not enough oil in the compressor
  • Insufficient or too much refrigerant
  • Air gap with the compressor clutch

What you can do if your AC clutch won’t engage

What you can do if your AC clutch won’t engage

To enable your AC clutch to re-engage, you may try doing these troubleshooting techniques:

Check the compressor’s oil levels

You may check your AC compressor oil level on the display glass thru a red line. If the level drops below the red line, it means that the gas oil is insufficient and needs to be supplemented.

Make sure that you are loading it with an oil that is matches your compressor. Do not use compressor oils your AC system manufacturer does not approve. You may check your AC’s user manual for specifications.

Get rid of overcharged refrigerant

Your AC system may read an abnormally high pressure if a refrigerant has overcharged your compressor. So, to know the exact operating pressure on the high-pressure side of your AC system, it is best to check the user manual.

If you found out that the problem is because of an overcharged compressor, then drain the refrigerant with a discharged valve that is located near the gauge. Let it bleed until it reaches the right level of pressure.

Add refrigerant

Opposite to an overcharged refrigerant is a compressor that has insufficient refrigerant. Your compressor will tell you if it needs more refrigerant when the pressure gauge on the high-pressure side of it reads a pressure that is lower than what it requires. Please check your car’s AC manual to know its right level of pressure.

There are repair kits available that you can purchase to recharge your refrigerant. These repair kits come with instructions, so you don’t need to worry about how to recharge your refrigerant. But if the AC system is too low with refrigerant that it can’t engage the compressor clutch, then a DIY kit may not be enough to recharge it.

If there are air and moisture in the system, it probably leaks. Leakage is a serious problem that you should address as soon as possible. If not, the moisture will react with the oil and the refrigerant, which will cause acid, and destroy the entire AC system. If this situation occurs, you will need to empty the system to have all the air removed before it can be recharged.

Read also: What Happens When There is Oil in The Coolant Reservoir?


Car inspectionDiagnosing the problem with your AC compressor clutch is not a complicated thing to do. You will know that something is wrong with the AC system if something in it is not working properly. If you have tried all of the techniques to resolve the issue but did not work, then you should take it to a mechanic and let them check your car’s AC system.

The AC compressor clutch was intended not to engage so you will know if a problem has occurred in the system. Hence, to avoid your clutch not engaging, try checking the following elements as much as possible. These include your Fuse, Coolant or Refrigerant, and Compressor Oil.

May you find this article as helpful as we hoped it to be.

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