Car waiting conditioner compressor clutch not engaging

If you’re here, possibilities are you’ve tried come recharge her AC system and also found a compressor clutch no engaging issue. If so, try the troubleshooting techniques described here. This is a complete explanation of just how the device works. After ~ reading, walk to this article to learn just how to diagnose a compressor clutch problem.

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Before friend start, recognize the difference in between a clutch type AC compressor and also a clutch-less compressor

Late model vehicles usage a clutch-less change displacement AC compressor. This compressor don’t have actually a clutch. The sheave drives the compressor the entire time the engine is running. When the AC isn’t on, the wobble plate inside the compressor is in the 0° position, therefore the compressor isn’t compressing any kind of refrigerant.

Older vehicles have a clutch form compressor. The wheel spins the entire time the engine is running, but the clutch bowl is stationary when the AC is off. As soon as the AC is turned on, power flows to the clutch coil, developing an elector-magnet that pulls the clutch plate against the pulley, which drives the compressor shaft.


The three materials of a car’s air air conditioning compressor clutch

Turn the air air conditioning controls to MAX AC and also start the engine. Climate look in ~ the prior of the compressor clutch. Both the pulley and also the clutch need to be spinning. That means the clutch has actually properly engaged with the pulley. If just the wheel is turning, but the clutch bowl isn’t, there’s a problem somewhere in the system.

Why AC clutch won’t engage

If the clutch doesn’t engage, the problem can be a puffy fuse, an open up in the wire to the clutch coil, a negative clutch coil, a negative ground, a low press switch lockout, or also a poor engine coolant temperature switch.

AC clutch not obtaining power

An AC compressor clutch relay can switch strength in a number of ways.

• from the low pressure switch. Once the low push switch look at refrigerant pressure above the low press limit, it close the door a move to complete ground come the AC compressor clutch control coil. The manage coil energizes and closes the relay contact to administer power come the AC compressor clutch coil.

• indigenous the PCM. The PCM/ECM monitors the low and also high press switches and if the pressures space withing spec, the PCM/ECM provides ground to the AC compressor clutch relay manage coil .The regulate coil energizes and closes the relay contacts to administer power come the AC compressor clutch coil.

In both of these scenarios, you’d begin the diagnosis by checking the compressor clutch fuse.


In some vehicles the compressor clutch relay is turned on and off by the low press switch and the evaporator temperature sensor.


In a computer system controlled system, the compressor clutch relay is grounded by the computer.

If the fuse is good, disconnect the electrical connector indigenous the compressor clutch coil. Move it far from relocating parts for this reason you deserve to safely examine for power and ground. Through engine running and the AC set to MAX, use a digital voltmeter to check for battery voltage and great ground at the connector. NOTE: part vehicles only have a strength wire going to the clutch coil. The clutch coil floor is interior to the compressor

If you’re not acquiring battery voltage in ~ the connector, pull the compressor clutch relay and check because that power and also ground ~ above the relay manage coil terminals in the socket.

If you view battery voltage ~ above the compressor clutch connector, then the difficulty is in the clutch itself.

Is the compressor clutch wait gap collection properly?

The compressor clutch air gap is critical to the AC compressor clutch engaging. Come learn an ext about AC compressor clutch waiting gap, review this post

Never jumper throughout the low pressure switch?

Air air conditioning compressors require a consistent supply of oil to stop catastrophic failure, and also it’s the refrigerant the carries the oil with the system. That’s why auto makers install a low pressure switch–to stop the compressor from running if the mechanism is short on refrigerant.

DIY recharging kits tell you come recharge v the low push port while the compressor is engaged. Yet if the mechanism is low on refrigerant, the clutch will never ever engage. Part DIYers think they deserve to just jumper the low press switch to pressure the compressor clutch to interact while they recharge.

THAT’s A poor MOVE. If friend jumper across the low push switch with tiny to no refrigerant in the system, you’re usually running the compressor with tiny with no lubrication. Would you run your engine through no oil? Well, the very same thing uses here. Friend may obtain the compressor to accept a charge, but you’ll it is in damaging the internal materials in the process. NEVER shot to bypass the low press switch. Doing for this reason will force the compressor to operation with insufficient oil and can damage the compressor.

Is the AC system too short to charge?

If an waiting conditioning device is so short on refrigerant that it can’t interact the compressor clutch, it’s really also low to it is in recharged through a DIY kit. If the push is listed below the low pressure switch limit that way you have actually a big leak and also there’s air and also moisture in the system. If you try to to fill the device with the waiting an moisture still inside, it’ll never ever work properly. The humidity will reason the growth valve or orifice pipe to freeze. And also the moisture will react v the refrigerant and also oil to reason acid and also sludge that can ruin the system. Wait in the device will reduce cooling, also if the fee pressures look at good. You’re no doing yourself any favors by forcing refrigerant right into a leaking system.

Can you check an AC fee level with the gauge ~ above a DIY kit?

Not really. DIY kit come v a low-pressure side gauge and they’re designed to provide a static push reading (engine no running or AC off) and a running push reading.

But the push readings alone can’t tell friend the refrigerant charge. Girlfriend must likewise know the ambient temperature. In fact, if you view a static push reading that 50-psi. All that tells girlfriend is the there is part refrigerant in the system. But unless you describe a temperature push chart that analysis can’t tell girlfriend if the system is short on charge.

What does a low-pressure gauge static reading tell you?

The only thing a static reading without correlating it come temperature have the right to tell friend is:

a) Your device is totally empty (0-psi.), or b) There’s sufficient pressure in the mechanism to over-ride the low-pressure cutoff switch. Period.

How to charge an AC compressor even if compressor isn’t running

You have the right to add much more refrigerant come the device without hot wiring the low-pressure switch and running the compressor. It’ll just take a lengthy time.

Connect the recharging kit come the low-pressure (suction) port. The low-pressure pipe is constantly a larger diameter than the high-pressure line. Plus, the DIY kit fitting will only affix to the low-pressure port. Rotate the vital to the operation position and turn the blower fan to HI. Rotate the AC come MAX to begin the radiator fans. Climate start including refrigerant.

If your auto is an orifice tube system, the refrigerant gas will flow through among the open up compressor reed valves and into the condenser coil. The radiator fans will cause the refrigerant to condense and also turn back into a liquid. The won’t it is in under pressure since the compressor isn’t running. Yet chances are several of the refrigerant will certainly still with the orifice tube and flow right into the evaporator coil. V the blower pan running, any liquid that enters the evaporator will certainly boil and also turn ago into a gas. After a few minutes, friend may have the ability to build up sufficient pressure come close the low-pressure switch. Therefore try starting the engine and also checking the compressor.

If you have an growth valve system, the blower fan will avoid the sensing tube from shutting under the expansion valve when you try to include refrigerant.

If this method doesn’t work, take it it come a shop. Perform NOT hotwire the low-pressure switch.

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Air conditioning compressor and clutch assembly

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