AC Compressor Clutch Not Engaging: 8 Prevailing Culprits

Failed AC system due to the AC compressor clutch not engaging can leave you unsettled, notably during the sweltering summer months. Indeed,  it’s dreadful if one of the AC system’s backbones gets ruined, as the compressor clutch is responsible for compressing the refrigerant and circulating cool air. 

Lucky you, diagnosing and fixing the issues are not that rocky, and you absolutely can DIY. To begin with, track down the root causes with DriveRevolve!

AC Compressor Clutch Not Engaging: Why?

Long story short: The AC clutch engagement often stems from electrical issues. Granted, the culprits may vary from vehicle to vehicle, including the bad clutch relay, blown AC clutch fuse, lousy switches, broken wiring, low/high refrigerant charge, and bad AC clutch itself.

Blown AC Clutch Fuse

Once the fuse controlling the clutch has blown, the AC clutch doesn’t turn on or engage. You have to find out what ruins your fuse. Perhaps, a broken clutch assembly or a corroded hot wire can provoke this.

Poor Relay

The relay controls the AC clutch in most autos. However, a sticking or malfunctioning relay may cut off power to your clutch’s coil, making the clutch unable to engage correctly.

Faulty Switches

To function correctly, the car’s AC requires a handful of switches. They control the flow of electricity and ground delivery to your AC clutch directly.

Some part-and-parcel switches are evaporator temperature sensors and high-pressure and low-pressure switches. Once one of these fails, your AC clutch can turn inoperable.

Wrong Wiring

Generally speaking, an air conditioner’s clutch assembly receives power and ground via a pigtail of wiring from the engine’s primary wiring harness.

The compressor clutch won’t engage if any wires in this circuit are open. Still, sometimes the wiring itself is functioning, yet the harness is flawed.

Insufficient Refrigerant Charge

When the system pressure drops too low, the low-pressure switch disconnects power and ground to your AC clutch. 

Consequently, if your compressor clutch isn’t working accurately, it may be time for a freon recharge.

Too-much Refrigerant Charge

The clutch on an AC’s compressor is shielded from damage by a high switch pressure disconnecting power and ground mechanism in the case of an over-pressure situation.

In other words, the AC compressor won’t kick on if overcharging the system with refrigerant takes place and causes the high-pressure switch.

Faulty AC Clutch Plate Or Poor Coil

The clutch assembly of an aging compressor may become less efficient over time. When the face on the AC’s clutch plate wears down, the clutch shall begin to slip.

Another reason an air conditioner’s clutch assembly is not engaging is a weak coil.

Ways To Manually Engage Your AC Compressor Clutch

Here comes a list of steps to manually activate the clutch:

Detach The Wiring Pigtail

First and foremost, locate the pigtail wire connecting to your compressor’s clutch assembly and detach it. It typically lies behind the AC, towards the compressor’s front end.

Pinpoint Power & Ground Wires

Checking the connector’s ground pins and power is the next step. In the event of uncertainty, a wiring schematic should be referred to.

Adjust Jumper Wires

Connect the power and ground terminals of your compressor’s control circuit using jumper wires. Settle an inline fuse in your jumper wire using your circuit’s positive side. 

Beyond that, your battery’s terminals may be swiftly and simply connected to these jumper wires’ supply end thanks to the addition of alligator clips.

Connect Your Jumper Wires

Mount the fused jumper wire between the battery’s positive post and the clutch coil’s positive wire. Similarly, settle the remaining wires between the battery’s negative post and the clutch coil’s negative wire. 

Interpret Outcomes

Based on your findings, you can tell if the AC clutch is broken. While jumping, your compressor fails to help the clutch to engage; it’s time to get a new one. 

Once your clutch is engaged, the plate at the back of the assembly will move abruptly and audibly “click.” Of note, if the clutch engages while jumping, the problem is in the system’s control circuit and needs further investigation.

How To Test Your AC Compressor

Inspect Your Power Source

Wait at least 10 mins after turning the automobile off before checking the air conditioner compressor. Verify the fuse’s position and a live power supply in the circuit with a multimeter in voltage DC mode.

Connect Ground To Your Compressor Relay

First, ground one of your multimeter’s leads, then hook up the multimeter to the compressor relay. As such, you can test the various components simultaneously and reckon the electrical current flowing.

Test The Wire Resistance Leading To And From Your Relay

Adopt your multimeter and switch it to the ohms setting to check the wires’ resistance to and from your relay. The reading should be 0.5 – 2 ohms for a well-functioning system.

Examine Voltage At Compressor Clutch’s Terminals

To achieve this, just connect the leads of your multimeter to the compressor clutch’s terminals when in AC mode. Based on the tested car’s model, there should be around 10 and 16 volts. If it’s lower than that, something’s wrong with the wiring or the compressor.

Examine Grounding Wire

Finally, ensure your vehicle’s ground wire is firmly fastened to the termination under your hood. A simple multimeter test in DC mode should reveal no voltage if the connections are sound.

This is how to check the health of your car’s AC compressor. Consult a professional technician if any of the readings seem off; this could indicate that a part needs changing or fixing.

Ways To Tackle A Compressor Clutch That Cannot Engage

Inspect Your Oil or Refrigerant Levels

Looking at your refrigerant levels is the quickest and easiest test. This is almost often the root of the issue regarding auto air conditioning. Check for an excess or deficiency in refrigerant using the sound gauges. The clutch might not disengage for multiple triggers. 

A do-it-yourself repair kit will have you back up and running in no time. Still, we advise having experts with the proper equipment handle this because, in certain areas, attempting this on your own might even be against the law. Hence, checking relevant local regulations is a must.

If the refrigerant is not the issue, a low oil level may necessitate a replacement. 

In some cases, your vehicle won’t start even after getting gas. Learn about why and what to do!

Reckon Voltage To Your Clutch

Measuring the voltage supplied to the clutch coil is the quickest and most straightforward method of detecting AC clutch issues. Although a ground cable may also be present, most vehicles only have a +12v cable leading to your AC socket.

After starting your engine, activate your air conditioning system, then disconnect the AC clutch connector. If all components function as they should, a multimeter reading is of 12–14 volts on this wire. Also, ensure the ground is secure when there is a ground wire.

A faulty clutch coil, a corroded clutch connector, or a broken AC clutch wouldn’t produce the correct volts and ground. Also, with no voltage present, check for other corners.

Jump Start Your AC Clutch

If the clutch doesn’t engage by hand, give it a jump start. You shouldn’t try this unless you know exactly what to do since you risk breaking pricey components otherwise. Get the proper wire by consulting a diagram of the circuit.

This is done by connecting the clutch’s wire straight to your battery. The clutch will need changing if this doesn’t get it going. In most cases, though, replacing the compressor in the AC is the superior option. 

Manually engaging the clutch indicates more unusual problems. Instead, you may have to replace a pressure switch, change a blown fuse, or mend a loose wire.

Inspect/Replace Your Fuse

Locate the correct fuse before getting it fixed. The service handbook for your vehicle should provide a schematic to help you. Turn off your engine before commencing.

Seek the proper fuse and employ a multimeter to ensure it’s working. Get the replacement once it gets blown.

Even so, if there is a more significant electrical issue, the fuse may blow even after changing. You must also adopt a fuse with the correct amperage while replacing the old one. 

Check High and Low-Pressure Switches

Next, inspect the AC system’s low and high-pressure switches. Usually, a multimeter will suffice to test these. You’ll need a repair manual tailored to the vehicle’s design if you want to know which figures to look for and when to close or open your circuit.

Pressure readings from these sensors can be viewed on an OBD2 scanner. Indeed, this device is prevalent in many modern vehicles.

Irrespective of a car that won’t start with a jump or AC compressor clutch engaging, referring to the experts is needed if the DIY method is in vain.

Set An Eye On Electrical Connections

The following step assesses the electricity connection since the AC clutch calls for power to function. The AC clutch’s power wire should be your first stop.

Visually check the rest of the system’s wiring, yet this one should be fine. If a wire or plug is broken, change it right away. 

How About The Cost To Replace AC Compressor Clutch?

A new clutch for an air conditioner compressor typically costs between $589 and $640. The price of labor is estimated at $180-227, while the cost of parts is $409-414.

Above is just the approximate figures; the actual values may vary based on different shops and years.

In A Nutshell

Summer heat can be unbearable without a functional air conditioning system in your car. So, it’s daunting that your car’s cooling system may be in trouble with the AC compressor clutch not engaging.

Now you should grasp all the triggers of the AC compressor clutch failure and the troubleshooting process to help you get your vehicle’s cooling system back up and running. Seeking professional help when you’re low to have things done independently. 

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