Simple guide on what to do when AC compressor clutch isn’t engaging

Updated Mar 10, 2021 | Same topic: Handy Maintenance Tips

Summertime is near.

What is an AC compressor clutch?

A car comes with a complex air conditioning system to provide the cabin cold or hot air depending on the settings dialed by the passengers. In an air conditioning system, one of the components that the system includes is an AC compressor.

Easy A/C Clutch Coil Test A/C Clutch Not Engaging

As the name suggests, an AC compressor compresses the refrigerants before going to the condenser and into other components and back to the compressor. An AC compressor receives power from the engine to function with the help of the drive belt and its clutch.

The AC compressor clutch is used to engage the power from the engine to the compressor. If your air conditioning system is turned off, the clutch is not engaged, hence the AC compressor is not driving.

Once you turned your air conditioning system on, the AC compressor will start rotating by engaging the clutch. This is the reason why you hear your engine makes louder noises after turning the A/C on.

Components under an engine bay

An AC compressor is driven by the serpentine belt alongside other accessory parts [Photo: CarTreatments]

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What makes an AC compressor clutch engage?

Inside an AC compressor, three main components are essential in operating the AC compressor. These components include the clutch, pulley, and clutch coil. As said earlier, the clutch is used to connect the AC compressor to the drive belt by engaging the pulley.

A pulley is a free-spinning component built with a bearing that is consistently spinning since it is connected to the drive belt. However, it is not consistently moving the AC compressor unless the clutch engages it to the AC compressor with the help of the clutch coil.

The clutch coil consists of wires that pull the AC compressor clutch to it if you turn the A/C on in the cabin. The pulley is then sandwiched by both the AC compressor clutch and the clutch coil which ultimately results in operating the AC compressor.

If your AC compressor clutch is not engaging, then your A/C will not work since it is the one responsible for compressing the refrigerants to the whole system.

Hand checking air temperature

Malfunctioning AC compressor will not provide the cabin cold air

Why is my AC compressor clutch not engaging?

Cause #1: Blown fuse

A fuse is used to blow when too much voltage is sent through the AC compressor system lines. If it is not blown, then it could also be burnt which provides the same results.

Too much voltage induced in your car components will them to be damaged, hence a fuse is installed in the fuse box usually placed near your car’s battery.

You can check the fuse of your car’s AC compressor if it is working or not by using a multimeter. Turn the engine off first before removing the fuse for the AC compressor.

Check if both ends are still electrically connected with a multimeter or other devices. If it is still working, then you can look for other possible causes of your AC compressor clutch not engaging.

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Cause #2: Incorrect amount of refrigerants

An AC compressor comes with two A/C lines that are essential in keeping the system in working order. These include the low-pressure A/C line and the high-pressure A/C line.

These two A/C lines are connected to each of their pressure switch that opens when an insufficient amount of refrigerants are detected.

As such, it is important to fill the right amount of refrigerants only. Both excess and insufficient refrigerants will cause the pressure switches to open which causes your AC compressor clutch to disengage.

This is made by car manufacturers for safety reasons so an imbalance in refrigerants will not blow your A/C system.

Cause #3: Lack of oil

Lubrication is also essential in keeping an AC compressor working. If your car’s AC compressor is low on oil, chances are it will heat up so fast resulting in wearing the load-bearing surfaces. A worn-out AC compressor clutch will not completely engage itself to the pulley causing your A/C to stop functioning.

An AC Compressor

A more in-depth look at an AC compressor [Photo: Spectra Premium]

How to examine if the compressor clutch is working?

To examine if your compressor clutch is working, you can set your A/C settings in the cabin to the max settings and look at the AC compressor under the hood.

If you see that the compressor clutch is spinning, then it means that it is working. The compressor clutch will stop spinning at times which is normal so it will not override the system.

You can also check the fuse if it working or not using a multimeter. Fill in the right amount of fluids required in the A/C system including oil and refrigerants.

Check the compressor clutch under the hood to see if it is spinning alongside the pulley. It is usually placed at the lower part of the engine bay so you might want to bring something to illuminate the compressor clutch.

A/C in max settings

Put your A/C to max settings to examine whether the clutch is engaging

>>> Related: 4 most common car air conditioning problems & How to fix them

How to manually engage AC compressor clutch?

The first and most common way to engage the AC compressor clutch is to add more refrigerants. An A/C system comes with various pressure switches that open and close depending on the number of refrigerants present in the system. Putting too much or an inadequate amount of refrigerant will cause your AC compressor clutch to disengage.

If all of the components are working properly, then it could be that the compressor clutch is already worn out and needs to be replaced. A worn-out compressor clutch won’t engage the compressor itself as it doesn’t make contact with the pulley properly. The replacement costs for an AC compressor will be around Php 12,000 for the component alone, depending on the model.

Woman putting clothe on her head

Keep your AC compressor in good condition to maintain a good cabin temperature while on the road

AC Compressor Clutch: FAQs

Q: What are the components used to engage an AC compressor?

An AC compressor uses a clutch, pulley, and a clutch coil.

Q: How long do AC compressors last?

AC compressors tend to last for around eight to ten years.

Q: What is a pulley in an AC compressor?

A pulley is a free-spinning component that is used to transfer the power from the drive belt to the compressor.

Q: How much is an AC compressor in the Philippines?

The price for an AC compressor ranges from Php 8,000 to Php 14,000, depending on the model.

Q: What is a clutch coil in an AC compressor?

A clutch coil pulls the clutch to engage the pulley to power the compressor.

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Rex Sanchez

Rex Sanchez


Rex Sanchez grew up in Saudi Arabia where he saw and got into the automotive scene. He started his career for an aviation company in the said region, writing about turbines and rotors which are later distributed for educational purposes. And now, he joined as a staff writer. Currently, he is the youngest on the team and is more than ready to grow in the field.


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