AC compressor clutch not engaging

AC compressor clutch not engaging (causes and how to fix it) 

If your AC compressor clutch is not engaging, it could be the result of other faulty parts. However, power is sent to the magnetic coil of the A/C compressor clutch when the vehicle’s A/C system is required to start up. By drawing the clutch’s drive plate forward, where it meshes with the clutch body and compressor pulley, this energization of the clutch coil produces a magnetic field that improves clutch engagement.

AC compressor clutch not engaging

The clutch of an A/C compressor transfers all of the rotational force generated by an engine’s serpentine belt to the compressor’s driveshaft when it is in the “on” or “engaged” state. However, the associated clutch coil is de-energized when the vehicle’s A/C system is turned off. The A/C system clutch then disengages. If the refrigerant in an air conditioning system is low, a clutch may engage and disengage alternatively.

However, in this article, you’ll get to know some of the things that could be causing your AC compressor clutch to stop engaging. You’ll also get to know what the grip is meant to do, how to diagnose it, and how to fix it.


What causes the AC compressor clutch not to engage?

Below are some of the things that could be causing your AC compressor clutch not to engage:

incorrect amount of refrigerant

The proper amount of refrigerant is required for the air conditioning system to function. Although the issue could be brought on by either too little or too much refrigerant. The modern system utilizes an AC pressure switch lockout mechanism to protect the valuable components if the refrigerant level isn’t correct.

However, the power provided to the AC compressor clutch will be cut off, and the clutch will not engage if the pressure in the AC system is too high or too low on either the low-pressure side or the high-pressure side. Although the AC refrigerant system may have been overfilled by you or another person if the AC pressure is excessive. if the pressure is abnormally low, the AC system is certainly leaking.

Damaged or Worn Clutch

It might just be that the AC compressor clutch has worn out, just like any other clutch, and needs to be replaced. Older cars or those that have overused their air conditioning system are more likely to experience this issue. When the clutch is newer, it won’t typically wear out. The clutch might not engage if the clutch plate is worn out.

However, it might occasionally slip, causing operations to be irregular. Some spacer shims in AC clutches can be removed in order to give the clutch a little bit more life. It might possibly be the result of a clutch coil failure, in which case the clutch coil won’t engage at all.

Failed high or low AC pressure switch

Another thing that could be the reason behind your AC compressor clutch not engaging is a failed high or low AC pressure switch. The AC system has two AC pressure switches: one on the high-pressure side and one on the low-pressure side. These switches regulate the pressure to prevent it from going too high or too low. Even if the pressure is correct, a malfunctioning sensor may send the wrong signal to the AC compressor clutch and cause it to shut down.

Bad electrical connection

The electrical connections and wiring in your car’s AC system are many. The clutch could stop functioning if there is an issue with any of them. The 12V+ power wire to the AC clutch is the most crucial connection; if the wire is corroded or damaged in any way, the clutch won’t engage.

Blown Fuse

AC compressor clutch not engaging can also be a result of a blown fuse. The compressor may get too much voltage if there is an electrical fault in the AC system. The fuse will blow as a result of this operation. It is better for the fuse to blow than for the system to receive too much voltage. If it occurred, the pricey AC components might suffer significant damage. The fuse for the AC clutch can be found by checking your owner’s manual.

The faulty or leaking evaporator coil

The evaporator coil is a component of the car’s air conditioning system that aids in airflow to cool the vehicle. Thus, if the coil is faulty or leaking, it could result in the AC compressor clutch not engaging. When the heat and air conditioning are turned on, a hissing sound or bad odor indicates that the evaporator coil is faulty or leaking. The clutch will not engage as a result. You might need to swap out the evaporator coil to resolve the problem. But keep in mind that replacing something costs a lot of money.

What is the AC compressor clutch meant to do?

The air conditioner compressor clutch is a part of the vehicle’s air conditioning system and is meant to engage and disengage the compressor pulley from the compressor drive. A magnetic switch is typically used to control it. The clutch is powered after the AC is turned on. This causes the compressor drive’s armature plate and compressor belt to engage, causing the compressor drive to rotate alongside the vehicle’s engine.

A friction plate and an electromagnetic coil make up the clutch. When the clutch is engaged, current flows through the coil, producing an electromagnetic force. The pump rotor receives power from this force, which pulls the coil in the direction of the friction plate and keeps the compressor operating. The clutch loses electrical power if the AC is turned off. Without this power, the compressor belt and armature plate disengage, which makes the clutch inactive.

How to diagnose why the AC compressor clutch isn’t engaging

You should turn the A/C settings in your car all the way up to see if your AC clutch is functioning. Then, turn on the engine and look under the hood to see the air conditioner compressor. The pulley and ac clutch spinning shows that everything is in order. There is a problem with the system if all that spins is the pulley. However, one of the causes listed above could be the culprit.

Check the condition of the belt covering the pulley on the compressor. If the belt is slipping or worn, it needs to be adjusted or replaced. Examine the area around the clutch plate for signs of rust. If you find any, the compressor may simply need to be replaced because it is old, worn out, and broken.

Check the wiring to the clutch because improperly connected wires could affect how the compressor operates. To supply enough power, the wire must be connected and in good shape. (In addition, the evaporator temperature sensor and high-pressure switch may be broken or have loose wires.) Your AC compressor’s fuses could be found in the fuse box. A fuse that has blown can be quickly replaced.

How to fix an AC compressor clutch that fails to engage

Here are things you should do to fix the AC compressor clutch that fails to engage:

Examine the refrigerant levels and make a correction

It is wise to start here because this is often the most prevalent issue with automotive air conditioning systems. To check whether the system has too little or too much refrigerant, use specialized gauges. The clutch might not disengage in either case. You can recharge the system to the appropriate levels using a DIY repair kit. We do, however, highly suggest that this be carried out by professionals using the proper equipment.

Measure the voltage transferred to the AC clutch

Measuring the voltage transferred to the clutch coil is the easiest method for diagnosing an issue with the AC clutch. The AC connector in the majority of car models simply has a +12 volt cable, but occasionally you can also discover a ground cable. The steps are straightforward: start the engine, turn on the AC, and unplug the AC clutch connector.

If everything is working as it should, you should observe 12 to 14 volts coming to this wire when you use a multimeter to measure the voltage going to the connector. You should also check the ground if there is one. If the proper voltage and ground are visible, you can determine that the issue is either a worn-out AC clutch, a defective clutch coil, or corrosion in the clutch connector. Continue troubleshooting if there is no voltage.

Check the low and high AC Pressure Switches

The AC system’s high-pressure and low-pressure switches need to be examined next. A multimeter can frequently be used to measure them in order to check them. But you need to get a repair manual for your specific car model to know what values to look for or when the circuit should be closed or opened. In some cases, an OBD2 scanner can be used to diagnose the AC system in newer cars, and in this situation, the diagnostic tool can display the pressure that these sensors measure.

Jump-start the clutch

To test whether the clutch will engage manually, you can jump-start it. However, you shouldn’t attempt this until you are certain that you understand it completely, since if you do it incorrectly, you risk damaging valuable parts. To be sure you are using the correct wire, use a wiring diagram. You would directly connect the clutch’s wire to the battery to complete this procedure.

If this is unsuccessful in engaging the clutch, a new clutch must be installed. However, installing a new AC compressor is typically the better choice. You may encounter some more uncommon problems if the clutch is engaged manually. Instead, you might need to rectify an electrical connection, replace a blown fuse, or install a new pressure switch.

Inspect the electrical connections

Another thing that could cause an AC clutch not to engage in either a mix-up in connections or damaged wires, as we discussed above. Connections should be checked, as the AC clutch needs an electrical connection to function. Inspecting the power wire to the AC clutch is the best place to start since if power cannot get to the clutch, it won’t engage. The remaining wires in the system must be visually inspected in addition to this connection. Any wire or connector that has been damaged should be replaced right away.

Check for any blown fuses and replace

Finding the correct fuse for the system is necessary before you can check the fuse. You should be able to find a diagram in the service manual for your automobile. With the engine off, carry out the following procedures: Use your multimeter to test the functionality of the fuse once you’ve located the right one. The only thing you can do if it blows is replace it. However, a more serious electrical issue could cause the fuse to keep blowing. It’s crucial that you replace the fuse with one of the right amperages.


What tells the AC clutch to engage?

When it is powered, the clutch oil begins to energize. The clutch is drawn in by a magnetic field and engages the compressor shaft as a result. Your car’s A/C compressor won’t be able to pump refrigerant as it should if the clutch fails to engage.

How do you force an AC compressor clutch?

Take the fused jumper wire and attach one end to the side of the wire connector that was attached to the compressor. The battery’s positive terminal should receive the other end of the jumper wire. It will give the compressor clutch battery voltage so that it can manually engage.

What controls the AC compressor clutch?

According to the graph, the compressor clutch has a special relay called a compressor control relay. Depending on the application, this relay can function in a number of different ways. One of the two fuses, which is fed by the relay and uses a 10 amp fuse, controls the coil in the relay.

What turns the AC clutch on and off?

Low refrigerant and a malfunctioning compressor are the two most typical reasons why the AC clutch in your car continually cycles on and off. You need to get a Freon recharge if the issue is low or leaky refrigerant. Low-pressure control on the compressor is activated by low refrigerant levels.

How do you tell if it’s the compressor or clutch?

The clutch does not spin when the AC is turned off. The clutch can make a short click as it starts to spin with the belt and pulley when the air conditioner is turned on. The compressor has to be serviced if the clutch does not engage or if it does so with a shrieking or whining sound.

What causes the compressor to not kick on?

  • Soiled condenser coils
  • Obstructed suction lines
  • Inadequate suction line size
  • Minimal refrigerant charge

Will the compressor clutch engage without Freon?

There won’t be enough refrigerant for the compressor to pressurize if the Freon levels are too low because the clutch won’t engage. In other words, there is nothing for your air conditioning system to operate with!

How do I reset my AC compressor?

  • Use the thermostat to turn off your air conditioning unit.
  • Look for the breaker box.
  • Your AC unit should be turned off at the breaker.
  • Before turning the breaker back to the “on” position, wait at least a couple of minutes.
  • Before turning your unit back on at the thermostat, wait 30 minutes.

Does the capacitor start the compressor?

The capacitor’s role is to supply 240 volts to start the compressor, fan motor, and blower motor when your thermostat instructs your air conditioner to cool the cabin. The capacitor will kickstart those components so that your air conditioner can start cooling outside air and blowing it throughout your cabin.

Will an AC compressor turn on if there is no refrigerant?

Without Freon or another refrigerant, the HVAC compressor cannot operate. The compressor has some cooling power and can function with little refrigerant. It is not advised to operate the air conditioner with insufficient refrigerant, though.

How do I know if my compressor isn’t pumping?

  • Your compressor is silent (quite obvious!). It should make a sound when it is running.
  • Circuit breakers frequently trip.
  • Warm air is coming from your vents (i.e., the condenser and blower fan are both working, but the central unit is not).

What kills an AC compressor?

Refrigerant loss is the main cause of a compressor’s early demise. An air conditioner’s refrigerant level is specifically calibrated to function with the compressor. The imbalance will eventually cause the compressor to overheat if the air conditioner leaks refrigerant.

That is all for this article, where we discussed some of the things that could be causing your AC compressor clutch to not be engaging. We also discussed what the grip is meant to do, how to diagnose it, and how to fix it.

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