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How To Manually Engage AC Compressor Clutch: The Easiest Methods

An automobile can have numerous serious problems and a dysfunctional AC compressor clutch is one of them. When this component does not work properly, the engine does not get the cold air flow – leading to some major complications. Knowing how to manually engage AC compressor clutch will help you skip a visit to the mechanic. Plus, you should also know how to examine the clutch to find out if it is faulty or not.

How To Examine The AC Compressor Clutch?

Using low-quality oil could be a reason for failing AC compressor clutch but it could happen even if you use synthetic oil and high-quality coolant. In a few cases, the clutch does not engage due to a clogged refrigerant circuit.

If you want to diagnose an AC compressor clutch for defects, apply these techniques:

Working Method 1

Set all air conditioning controls to the MAX before kicking off the engine. Check the front side of the clutch to examine its condition. Also, find out whether the clutch and the pulley are spinning. If only the pulley is rotating, the compressor clutch is having an issue, which could be stemming from several sources – a blown fuse, bad clutch oil, low-pressure lockout, or an open wire in the oil.

how to manually engage AC compressor clutch
Put the AC on MAX before checking the compressor.

Working Method 2

Before starting the next step of diagnosis, you should know that a low-pressure switch can create problems with the compressor clutch’s relay in some car models. The system’s computer keeps the relay grounded but it can go on and off due to the bad switch. A careful inspection of the system and its components will help you to pinpoint the source of trouble.

In this step, you have to detach the connector cable from clutch oil. Keep it safely away from all other components. Use a digital voltmeter to measure the ground and voltage of the battery at the detached connector cable. Go on to check the fuse if you cannot read the voltage readings. Move on to the clutch relay if the fuse turns out fine.

Working Method 3

In a few car models, the power of the air conditioning system flows from the AC switch to the fuse before being transmitted to the clutch oil through the low-pressure evaporator temperature. You have to make sure that the compressor has enough oil to function properly.

When you are sure that there is a problem with the clutch, the next part is to engage it. The next section tells you how to manually engage AC compressor clutch at home.

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How To Manually Engage AC Compressor Clutch

Engaging the AC compressor clutch at home is not rocket science. There are a couple of ways you can fix the problem to bring back the air conditioning system in order.

Method 1: Add More Coolant

What is the most common reason for an air conditioning compressor not to engage? Low level of refrigerant. When the coolant level in the system goes down, the low-pressure switch does not allow the compressor to rotate.

How to manually engage AC compressor clutch when the system is low on antifreeze? Easy. Just adding refrigerant will solve this problem. If your car is compatible with R134a type of refrigerant, attaching a can to the system will override the low-pressure switch and restore the normal function of the compressor clutch.

Tips – When you are going to manually engage the compressor, make sure that the system has enough oil. Inadequate lubrication can damage the compressor.

how to manually engage AC compressor clutch
Adding a can of coolant is the easiest solution. Source:

Method 2: Jump-start The Clutch

The process is a bit different for older cars that are not compatible with the R134a type. You have to jump-start it and the process won’t take more than a couple of minutes:

Examine the oil level in the compressor. Add oil if the level is below the normal point. Check the owner’s manual to check the correct instructions for checking up the compressor oil and level and filling it up.

Unplug the single wire connector on the front side of the compressor. Take the fused jumper wire and connect its one end to that side of the wire connector that was connected to the compressor.

Attach the other end of the jumper wire to the positive terminal of the battery. It will supply the battery voltage to the compressor clutch, allowing it to engage manually. There is no need to switch on the air conditioning system for this method to work.

Tips – You should route the jumper wire to avoid it getting tangled or interfering with other moving components.

Method 3: Replacing The Clutch

It is an ominous sign when the clutch engages but the compressor does not spin. Changing the compressor clutch could be the only solution in this case. A bad AC compressor clutch needs immediate fixing. A delay can cause serious damage to the air conditioning system and the engine.

  1. Ismail says

    I have just refilled my C202 AC……….now my fan turns on and off with some noise whenever i turn on the AC,what could be the problem.

  2. Ed Shnatter says

    I have an open coil. What’s your thoughts on grinding down the clutch plate so it’s always engaged to the pulley / always turns the compressor? I would leave it like that till the fall, then add a spacer or something so the clutch isn’t engaged.

    The car is a 2010 honda civic with 150K miles and has banged up bumper. So it’s worth maybe $2.5K? or $3K at most? So replacing compressor, which any garage I spoke to would do – they don’t want to replace parts on the compressor like coil… not worth their time? Afraid if there’s other issues, I’ll blame them…

    So I could do the clutch removal, grinding and replace. I’d leave the AC siwtch on all the time. Any downside? Bad for the car to start with compressor on? (too much load on the engine?). I don’t want to break something else (hence me not thinking I could do the coil replace successfully!)

  3. David says

    The Compressor is not meant to run all the time. That is why the clutch assembly is necessary. The computer can turn it on when needed, then off when it has done its job.

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