The Ultimate Guide to Manually Engaging an AC Compressor Clutch

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    For people with little to no experience (and patience) in repair work, the first plan of action when facing mechanical defects is to call a mechanic. While we truly know that the mechanics are the unsung heroes of our day-to-day automotive dilemmas, we must not fully rely on them (like your favorite fantasy superhero). Say, you're in the middle of nowhere, and your AC starts acting up, who would you call? You heard it right – yourself.

    Be your mechanic of the day and learn the basics of manually engaging your AC compressor clutch. Don't worry, and we have everything explained as less “mechanical” as possible.

    What is an AC compressor clutch?

    The AC compressor clutch is the first thing that moves every time you turn on your AC. Think of it as a switch that is responsible for engaging and disengaging the AC compressor pulley from its compressor drive.

    AC Compressor

    How does an AC compressor clutch work?

    Whether the clutch operates or not will all depend on the AC itself. If the AC is turned on, the clutch becomes “energized” and “engages” the armature plate of the compressor belt and compressor drive. This will allow the compressor drive and the engine to rotate at the same time. Hence, the AC starts working.

    turn on AC

    On the other hand, a “de-energized” clutch will “disengage” the compressor drive and the belt pulley. This will stop the AC compressor.

    Note that we have two main keywords here – “engage” and “energize.” By now, you might be wondering what these two words mean. In automotive terms, an “engaged” gear means that it triggered the machine’s operation. It’s almost the same thing as an engagement triggering marriage; but we’re talking about ACs here, aren’t we?

    Going back, our second keyword is “energized.” When a gear becomes “energized,” it is connected to its power source. Think of it the same way as you insert the TV plug into a convenience outlet if you want to watch TV.


    What causes an AC compressor clutch to stop working?

    Now that you’ve had an idea on how the AC compressor clutch works, let's get straight down to business. Since our main goal here is to engage the clutch manually, we must know what causes an AC compressor clutch to be faulty. Here are three reasons why:

    Reason 1: A blown clutch fuse

    By far, this is the most common. You must use a multimeter to check for this.

    Reason 2: A defective clutch relay

     To check this, unplug the connector at the clutch coil and turn on your AC. Then, examine its battery voltage.

    defective clutch relay

    Reason 3: The AC has too low pressure

    This could also mean a lower amount of refrigerant. This makes the AC compressor to run on little oil, which will result in a defective clutch.


    What are the symptoms of a defective AC compressor clutch?

    Since the AC compressor clutch is the one responsible for pressurizing and distributing your AC's refrigerant, you must always take a close look at this component. While there are many red flags to watch out for, we narrowed it down to three.

    Symptom 1: AC compressor clutch won’t engage

    An improper air gap or bad clutch oil may cause this problem.

    Symptom 2: AC compressor clutch screeches

    Again, it can be due to improper air gaps or rust accumulation in the clutch plate and pulley.

    Symptom 3: AC blows warm air

    There’s only one reason for this: a slipping clutch. As a result, your AC can’t provide the highest level of refrigerant compression.


    How should you manually engage your AC compressor clutch?

    With all the automotive jargons we’ve discussed earlier, you might think that learning how to manually engage the AC compressor clutch is true rocket science. The good news is – it’s not. Here, we have simplified three methods of engaging an AC compressor clutch all by yourself.

    Method 1: You can add more coolant

    As what we’ve mentioned before, one of the most common reasons for disengaging ACs is a low amount of refrigerant. How do you solve this? Simply add more coolant. If your AC is compatible with an R134a refrigerant, attaching it to your unit will overrule the low-pressure switch. This will result to a normalized function of your AC compressor clutch.

    add more coolant

    Method 2: Jump-start your clutch

    If your AC isn’t compatible with the R134a type and is actually an older model, consider jump-starting your clutch. This process will only take a few minutes if your AC compressor has enough oil.

    Now that we’re talking about oil, here’s a quick disclaimer: Always make sure that your AC is well fed with oil before doing any repairing. Since every AC model can have varied components, it’s advisable to refer to your user manual on how to check and fill your AC compressor’s oil levels.

    How do you jump-start your clutch? You only have to do three steps here. First, unplug the wire connector on the compressor’s front side. Second, connect the fused jumper to the same side where you unplugged your wire connector. Remember that it must also be connected to your AC compressor. Third, attach the other end of the fused jumper to the battery’s positive terminal.

    Since this method is all about supplying energy to the AC compressor clutch through the battery, no switches are needed for this to work. Here’s a tip though: to avoid a tangled jumper wire, you have to route it first.

    Method 3: Replace your clutch

     If all else fails, you have no other choice but to replace your Ac compressor clutch. This kind of contradicts with our main goal here, which is to resurrect the clutch.  

    However, we’re all about immediate solutions here. You have to replace an un-repairable AC compressor clutch right away to keep it from bringing any further damage to your unit.

    Replace your clutch

    Common car air conditioner problems

    You may also interest on common car air conditioner problems, the usual causes, and ways to diagnose them. Please read it.


    Our advice

    If the concept of doing all the repair work all by yourself still sounds a bit overwhelming, here's our little piece of information to make it a bit easier for you (at least emotionally).

    Start with the more straightforward solutions first – that is, carefully checking your AC compressor clutch and going back to method 1.

    We understand – you might find all of these enjoyable. However, try not to go too far, experimenting with preventing further damage. If you still can't manually engage your AC compressor clutch, a deeper problem that needs the expertise of a mechanic might be your best bet.


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