How To Fix Car 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 air conditioner 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 a car AC compressor clutch not engaging with a pressure chart in four minutes.

Related Post: Types Of Compressor Oil: Mineral, PAO, POE, PAG Oil

Car AC Compressor Clutch Not Engaging

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

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 not engaging” problem to show you how to fix AC in a car.

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

  1. Fixing AC problem Inside of the car (Interior Cabin)
  2. Fixing 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 the car AC compressor not turning ON. So, get ready. Let’s start.

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 ON the AC and blower motor.

2) Inspect The A/C Button:

AC Switch
AC Switch

Now, start fixing the car AC 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 AC 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 AC was turned ON. He thought that the AC 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 a leak occurs in the evaporator then there is a maximum chance that the car AC 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 AC compressor clutch does not engage.

Outside Of The Car (Under The Hood):

Now it is time to fix the car AC 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 AC under the hood is the compressor clutch. Does it sound click when the air conditioning is turned ON?

If it does not click, then look for connectors. Sometimes connectors get lost or become corroded, which prevents the clutch from engaging.

This is an Info
Case in point that sometimes a clutch engages and disengages, 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, as a result, the car AC compressor clutch will not engage. Therefore, check with fingers pushing down on the belt to look for belt tightness.

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 not engaging. Check for AC fuse especially looseness and blown fuse and also check for 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 AC 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 AC compressor 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 low and high-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 are 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 air conditioner.

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

Frequently Asked Questions (FAQs)

How do I know if my AC compressor clutch is bad?

There are a few ways to tell if your AC compressor clutch is bad. One way is to listen for a clicking noise when the AC is turned on. Another way is to feel a pulsing sensation in the AC lines. Finally, you can check the AC compressor itself for any leaks or signs of damage. If you notice any of these things, it’s likely that your AC compressor clutch is bad and needs to be replaced.

Can you replace the AC clutch without removing the compressor?

There is no definitive answer to this question as it depends on the specific make and model of the vehicle in question. However, in general, it is generally advisable to remove the compressor when replacing the AC clutch. This is because the compressor is typically located in close proximity to the clutch, making it difficult to access the clutch without removing the compressor. Additionally, removing the compressor allows for more access to the clutch, making it easier to replace.

Can I drive my car with a bad AC compressor clutch?

It is not advisable to drive a car with a bad AC compressor clutch. The AC compressor clutch is responsible for engaging and disengaging the air conditioning compressor. When the clutch is not functioning properly, it can cause the compressor to overheat, which can lead to engine damage. Additionally, driving with a bad AC compressor clutch can put unnecessary strain on the engine, which can decrease its overall lifespan.


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