How To Fix AC Compressor Clutch Not Engaging: 10 Steps

How To Fix AC In Car

Fixing a car AC system is sometimes very difficult because the same problem can happen for many reasons. Moreover, the same problem can be approached in many ways.

If your car’s cooling system isn’t working as well as it should be, there’s a good chance that the compressor clutch is not engaging. If this is the case, there are a few things you can do to try to fix the problem yourself.

Do you know the hardest part of troubleshooting a car, is knowing where to start? Here is how to systematically approach an AC problem.

In this powerful article, you will learn how to fix if a car AC compressor clutch does not engage with a pressure chart.

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What Is AC Clutch

Car AC Compressor Not Turning ON
Car AC Compressor Not Turning ON

In an automotive air conditioning system, the AC clutch plays a crucial role in regulating the temperature inside the car. It is a component that stimulates and stops the compressor, which is responsible for compressing and circulating the refrigerant gas in the AC system.

When the AC clutch involves, it allows the compressor to spin and start circulating the refrigerant gas, which is essential for the air conditioning system to function. The compressor works to maintain the desired temperature inside the car by compressing and circulating the refrigerant gas, which absorbs heat from the air inside the car and releases it outside.

 Importance of Air Conditioner Compressor Clutch

The importance of the AC clutch lies in its ability to start and stop the compressor as needed, based on the demands of the air conditioning system. This helps to regulate the temperature inside the car, making it more comfortable for the driver and passengers. Without a functioning AC clutch, the compressor would run continuously, even when the air conditioning is turned off, leading to increased wear and tear on the AC system and reduced fuel efficiency.

In conclusion, the AC clutch is a vital component in automotive air conditioning systems that allows the compressor to operate efficiently and regulate the temperature inside the car. Regular maintenance and inspection of the AC clutch can help prevent issues and ensure optimal performance of the air conditioning system.

Symptoms of AC Clutch Not Engaging:

If the AC clutch is not engaging properly, there are several symptoms that may be observed, including:

  • No cold air
  • Unusual noises
  • AC compressor not turning
  • Reduced cooling performance
  • Increased fuel consumption

Why My AC Clutch is Not Engaging: Common Reasons

The AC clutch is an important component of an air conditioning system that connects the compressor to the drive pulley. If the ac compressor clutch isn’t engaging, it may be due to several reasons.

  • Clutch Coil: The clutch coil, which provides power to the clutch plate, could be damaged or burned out, which can’t engage the compressor clutch. Also, check the electric wire in case of bad clutch coil symptoms.
  • Pressure Switch: One of the important factors is the pressure switch. The pressure switch, which senses the refrigerant pressure in the AC system, could be faulty, preventing the clutch from receiving its operational commands. So, also check the ac pressure switch.
  • Refrigerant Level: The low refrigerant level in the AC might not engage the compressor.
  • Electrical Issues: Electrical issues such as a blown fuse for the ac clutch or a damaged wire could also prevent the AC clutch from engaging.
  • Worn Bearings: The AC compressor can’t operate correctly with faulty bearings, as a result, the clutch will not engage correctly due to the restriction in the movement of the assembly’s clutch.
  • Expansion Valve: The AC expansion valve, which regulates refrigerant flow, could be clogged, causing the AC system’s pressure to be too low, and the compressor’s clutch fails to engage.

Overall, various factors are responsible for the compressor clutch’s issue, and it’s important to diagnose and fix the issue if ac isn’t working properly.

How To Fix An AC Compressor Clutch Not Engaging

Finding an air conditioning problem systematically becomes easy when fixing the car AC not turning on and off. Just to have a good understanding of troubleshooting and fixing an air conditioning fault. I will take the “car AC compressor clutch doesn’t engage” problem to show you how to fix AC in a car. There might be several reasons why your ac clutch is not working.

Before we dive into the troubleshooting process, for simplification purposes, I will divide the AC system into two sections.

  1. Fixing the AC problem Inside of the car (Interior Cabin)
  2. Fixing the AC Problem Outside of the car (Under the hood)

Here I am staring from inside of the car and giving you step-by-step instructions that how to troubleshoot if the compressor is having an issue when ac is turned on. So, get ready. Let’s start with the reasons why the ac clutch is having issues.

Related Post: How Car Air Conditioner Works

10 Easy Steps To Fix Car AC Compressor Clutch Not Engaging

Inside Of The Car (Interior Cabin):

1. Start The Engine And Turn ON The AC And Blower Motor:

First of all, start the engine and turn the AC ON and the blower motor.

2) Inspect The A/C Button:

AC Switch
AC Switch

Now, start fixing the car A/C problem with AC ON & OFF buttons. Press the AC button ON and turn the blower fan knob, and see if the light illuminates in the AC button, if not then this is a sign of a faulty switch or wiring problem.

3. Check For Cabin AC Air Filter:

Clogged Air Filter Of Car AC
Clogged Air Filter Of Car AC

Secondly, you should check the cabin AC air filter for fixing the car A/C compressor not turning ON. Sometimes AC turns ON but due to a clogged air filter, air can not bypass the air filter and you think that AC is OFF.

I remember, once a client had the problem of air does not blow out of the vent when the car’s ac system was turned ON. He thought that the AC set is defective. I checked the AC air filter and it was very clogged, not letting the air bypass. I install the new air filter and the problem was solved.

4. Check For The Leaky Evaporator:

Fully Clogged Evaporator
Fully Clogged Evaporator

Troubleshooting the evaporator is difficult. If there is a leak in the ac system then there is a maximum chance that the car A/C compressor will not turn ON. The symptom of the leaky evaporator is oily mist on the inside of the windshield through the defroster duck.

5. Check For Thermister:

Car AC Thermister
Car AC Thermister

Thermister is a temperature-sensing device fitted in the evaporator. It is an essential component of the car’s modern AC system. It tells the AC control module about the temperature of the cabin. A faulty thermister will not provide the module about cabin temperature and as a result, the car clutch of the cooling system does not engage.

Outside Of The Car (Under The Hood):

Now it is time to fix the car A/C compressor not turning ON outside of the car under the hood.

6. Look For The Compressor Clutch

Compressor Clutch, Pulley And Coil
Compressor Clutch, Pulley, And Coil

The first thing you should look into to fix a car A/C under the hood is the compressor clutch. The clutch present on the compressor shaft is responsible to engage and disengage the compressor. A wire to the clutch is responsible for providing a signal which produces an electromagnetic field. This magnetic field pulls the clutch, and power to the ac compressor is transferred when the clutch is engaged.

Does it sound clicks when the air conditioning is turned ON?

If it does not click, then look for connectors. Sometimes connectors get lost or become corroded, which is responsible for the clutch not to engage.

This is an Info
Case in point that sometimes a clutch connects and disconnect, often it is normal. But, there is just a thin line when it engages and disengages very quickly, this might be a sign of low refrigerant.

Related Post: Car AC Compressor

7. Check The AC Belt

Car AC Belt
Car AC Belt

The second thing you should check is to Inspect the AC belt tensioner. Sometimes the AC belt is loose, which cannot rotate the compressor pulley, and cause ac clutch not to engage. Therefore, check with fingers pushing down on the belt to look for belt tightness for the proper working of clutch and the pulley.

8. Check For AC Fuse And Relay

Car Fuse
Car Fuse

Fuse and relay have a huge impact on the car’s AC compressor’s clutch to engage. Check for AC fuse especially looseness and blown fuse and also check for compressor clutch relay such as a corroded relay.

Related Post: Ultimate Guide To Car Fuse

9. Check For AC Wiring

Shorted Wiring
Shorted Wiring

If everything is OK and still the car A/C compressor does not get power, there might be a wiring issue. Look for the AC compressor connector, it can get broken, corroded or sometimes the compressor ground connection gets corroded, as a result, the car’s clutch will not engage.

Related Post: Doing These Will Make Your Car AC Blow Twice As Cold

10. Check For Low And High Refrigerant Pressure

Low and High Pressure Port
Low and High-Pressure Port

First of all, find out the high or low ac pressure ports and install the pressure gauges and also check the pressure in both ports. In a low-pressure port, the pressure should be around 40 psi and in a high-pressure port, the pressure should be around 170 psi to 250 psi depending upon the car.

Below is the Temperature and Pressure Chart where you can see how temperature (Especially Under Hood Temperature) can affect refrigerant pressure on the high and low-pressure sides. You can take guidance from this chart to charge refrigerant in your cooling system.

Related Post: 3 Types Of Car AC Refrigerant, Freon R-12, R-134a, R-1234yf

Temperature And Pressure Chart

In this instruction procedure, I have given you a general idea that how to troubleshoot and fix AC in a car.

You can use this method with other AC-related problems.

Car AC Pressure-Chart
Car AC Pressure-Chart


In conclusion, an AC compressor clutch not engaging can be a major inconvenience for anyone. By understanding the causes, and symptoms, and how to fix them, you can take the necessary steps to get your air conditioning system running again. In some cases, it might require minor troubleshooting and the replacement of a few components. However, if the repair is more complicated or involves replacing the entire compressor unit, calling a professional may be the best option.

Frequently Asked Questions (FAQs)

How do you manually connect the clutch of the cooling system?

To manually connect the clutch of the cooling system, you can pull the compressor clutch relay or wire directly to the clutch coil. This will cause the AC clutch to engage, which will power the compressor belt.

What is an armature plate in an AC system?

An armature plate is a component in the clutch of the cooling system that connects to the compressor belt and rotates the compressor pulley from the compressor drive. It plays a critical role in the compressor’s operation.

Why does the AC clutch engage?

The AC clutch connects to provide power to the compressor belt, which drives the compressor and compresses refrigerant. Without the clutch engaging, the compressor would not be able to function properly.

What might be causing the clutch of the cooling system not to connect properly?

Several issues could cause the clutch of cooling system not to connect properly, including a mechanical problem with the compressor, a problem with the clutch receiving its operational commands, or an issue with the ac pressure switch lockout mechanism. It is crucial to determine the cause to ensure your AC is working correctly. One way to test this is by using a switch to force the compressor to run and check if the compressor clutch connects, or by checking for energization of the clutch coil or a signal to the AC compressor.

What might be causing the clutch on my AC compressor not to connect properly?

1. The clutch wire of the coil may be disconnected or damaged.
2. The open compressor reed valves may be preventing the clutch from engaging.
3. There might be an issue with the power wire to the AC clutch.

How can I determine if my clutch of cooling system is working properly?

1. Make sure your AC is working and set to its coolest setting.
2. Try running the compressor with little to no load on the system to see if the clutch connects.
3. Check the power wire to the AC clutch and make sure it is sending voltage when the AC is turned on.

Can I bypass the clutch of cooling system switch and run the compressor continuously?

1. Yes, but it’s not recommended as it can cause damage to the compressor or other components.
2. If you do choose to bypass the switch and run the compressor continuously, make sure you have proper ventilation and the system is not overloading.
3. It’s best to determine what is causing the clutch not to engage and fix that issue instead of bypassing the switch

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