Blog Car Care Advice Reasons Why Your AC Clutch Is Not Engaging (+ Solutions)
Car Care Advice

Reasons Why Your AC Clutch Is Not Engaging (+ Solutions)

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The AC clutch cues the compressor to release the refrigerant that cools your car. If it doesn’t engage, you’ll notice rattling noises and hot air blowing from the AC vents.

So, why is your AC clutch not engaging
Let’s explore potential causes that stop your car’s clutch engagement. We’ll also check out the ways to diagnose the core issue and a few possible solutions to fix it.

This Article Contains:

8 Causes That Stop Your AC Clutch from Engaging

While premature wear can stop an AC compressor clutch from working, it may malfunction due to other reasons like:   

  1. Faulty electrical connections: A blown fuse, failing AC relay (clutch relay), corroded wires, or low battery voltage disrupt the electrical continuity the clutch requires to engage. 
  1. Incorrect refrigerant levels: If there’s insufficient refrigerant, then the clutch won’t engage as a safety precaution. Conversely, excess refrigerant leads to a high-pressure environment, which will prevent the clutch from working.
  1. Compressor issues: When the AC clutch engages, the compressor shaft spins to circulate the refrigerant (like Freon) through the system. However, moisture and corrosion build-up in the AC system can hamper the electrical connection between the compressor and clutch.
  1. Bad clutch coil: This electromagnetic coil provides the magnetic force to engage the clutch. If worn out, it will fail to work.
  1. Malfunctioning pressure switch: The high and low-pressure switch signals the AC clutch to engage the compressor when there’s a change in refrigerant pressure. Each high and low-pressure sensor monitors the high side (between the compressor and the condenser) and the low side (between the evaporator and the compressor) of the AC system. If these switches or their sensors malfunction, the AC clutch won’t engage, and the compressor won’t function. 
  1. Loose or damaged belt: The serpentine belt transfers power from the engine to spin the AC compressor shaft. If the belt malfunctions, the compressor can’t spin, and the clutch won’t engage. 
  1. Failing control module: Without the latest software updates, the climate control module could fail to regulate the cabin temperature. It may also send improper signals, stopping the clutch from engaging.     
  1. Additional mechanical issues: Trouble with other AC system parts, such as a stuck pulley or worn bearings can prevent the clutch from engaging.  

Your car’s clutch engagement stops for several reasons. 
But how do you find the root cause? 

Let’s have a look. 

How to Diagnose a Bad AC Clutch?

Checking your AC controls without any experience can be dangerous, as you’ll be dealing with toxic refrigerant and an electrical fuse box. It’s best to have a mechanic handle it. 

Here’s what they’ll check during a visual inspection:

A. With the engine turned off, they’ll look for:

  1. A blown fuse that’s not providing proper voltage 
  2. The condition of the ground (a wire at the back of the clutch) in the clutch relay socket
  3. The battery voltage level
  4. Wear and tear of the drive belt
  5. Rust formation around the clutch plate
  6. Damaged or loose wires near the low and high-pressure switch as well as the clutch
  7. A leak from the AC system’s condensers and pipes 

B. Next, with the engine turned on and the AC button pressed, they’ll check if: 

  1. AC vents are releasing cold air 
  2. There’s a clicking sound of the clutch engaging and disengaging
  3. The serpentine belt turns the pulley smoothly
  4. The AC compressor spins properly​

Depending on the issue, the mechanic will perform an AC clutch repair or replace the parts.
Let’s check how they do it.

How to Fix a Faulty AC Clutch?

Here are some ways a mechanic will try to fix a failing AC compressor clutch: 

1. Refill the Refrigerant

The steps to refill the refrigerant (Freon) are as follows:   

  1. They’ll open the car’s hood and look for the refrigerant port (marked with the letter ‘L’) near the low side of the air conditioning system.
  2. Then, they’ll attach the refrigerant can to the port. 
  3. The mechanic will use a pressure gauge to check the refrigerant charge (fluid level). If the pressure reading is lower than required, they’ll adjust the refrigerant charge accordingly. 
  4. They’ll add the refrigerant by squeezing the can trigger in short bursts. 
  5. They’ll wait for 30 seconds and recheck the refrigerant pressure to avoid overfilling. 

2. Jump-start the Clutch

Sometimes, the AC clutch won’t engage even after adding the refrigerant. So, your mechanic will jump-start the clutch instead.

Here’s what they’ll do: 

  1. The mechanic will first check the oil level in the compressor. If the level is low, they’ll top it up.

    Note: Refilling the oil is vital as it lubricates and protects the air conditioning system’s parts from corrosion.

  2. The mechanic will locate the AC relay, which is usually in your car’s fuse box. 
  3. Next, they’ll check the pins on the relay socket that need to be connected to power the clutch.
  4. Then, they’ll connect one end of a jumper wire to the pin and the other to the battery positive. 
  5. With a jumper wire, the AC clutch can manually engage without needing a signal from the pressure sensor.  
  6. Then, they’ll start the car and turn on the AC to check whether the system is functioning.   

3. Perform a Replacement

If the clutch is severely worn, you’ll most likely need a replacement.

Here’s how a mechanic will replace your AC clutch

  1. Open the hood and disconnect the battery.
  2. Remove the plastic engine cover. 
  3. Loosen the drive belt and slide it off the AC compressor pulley. 
  4. Remove the clutch bolt holding the clutch assembly (which includes the clutch plate and the clutch coil.) 
  5. Finally, attach the new clutch piece and re-install the parts. 

Most manufacturers recommend replacing the clutch and AC compressors together to ensure stable performance. However, this will increase the overall replacement cost.

Curious to know more about the AC clutch? 
Let’s resolve any queries you may have.  

3 FAQs on AC Clutches

Explore these questions for additional information on AC clutches.

1. How Much Does It Cost to Replace an AC Clutch?

The average cost of replacing an AC clutch ranges between $590 and $650. The parts will cost between $400 and $420, while the labor charges will be between $180 and $240. However, your overall expenses depend on the car model and the repair shop you visit. 

2. How Long Does an AC Clutch Last?

While an AC compressor lasts between 10 to 12 years, the AC clutch can wear out earlier. Their overall lifespan will also depend on usage and the local weather. Running the AC on max power and driving in a hot climate will strain your car’s AC, reducing its lifespan. 

3. How to Maintain Your AC System? 

You can prolong the lifespan of your car’s air cooling system by: 

  1. Changing the air filter often 
  2. Refilling the refrigerant on a timely basis
  3. Parking under a shade to reduce strain on the cooling system
  4. Scheduling an engine maintenance service as per your manufacturer’s recommendations

Restore Your Car’s Cooling with AutoNation Mobile Service

Your car’s AC clutch activates the compressor, releasing the refrigerant that produces cold air for your car. If it doesn’t engage, you’ll be driving with a stuffy cabin that can ruin your driving experience.  

Don’t feel like driving to the mechanic without a working AC?
No worries! Our mechanics from AutoNation Mobile Service can fix your car’s AC system from your driveway. 

We’re a mobile auto repair solution that offers easy online bookings and a 12-month | 12,000-mile repair warranty on all services. 

Contact us to get your AC clutch fixed or replaced conveniently.