Honda A/C Compressor Thermal Protector

1999 Honda Civic. The compressor is a used one I installed a few years ago. The A/C has been working fine but after a drive, parking, and shopping it was blowing hot air. The compressor clutch was not spinning. Later, at home, after cooling down a while, the clutch did engage and the system blew cold air. The state of charge was OK, according to the gauge on an empty recharge canister I had kept.

I think the compressor thermal protector circuit was open until the car sat at home and cooled down a bit.


Is that thermal protector malfunctioning (how can it be tested, what is its open/closed temperature spec)?

Is the compressor actually overheating (why does that happen)?

What harm if I bypass that thermal protector (I’ll need another compressor anyway, if this one is overheating.) If it siezes up I’ll have to remove or cut the belt. On this car that belt is only for the compressor.

your compressor clutch might have a too big of a air gap. you can try cleaning all the rusty contact surface’s first. if that doesnt help you can take a look at this video before putting in another compressor to see if it works. you have nothing to lose if your planning on replacing it anyway.

1999 Honda Civic compressor air gap - Yahoo Video Search Results

on fords and some other vehicles they have different size spacers. you can take one or two out till you have the correct air gap thats specific to your vehicle. but it seems honda does not have the spacers.

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you need to look on line to see what the air gap space should be for your car. then use a feeler gauge to see if its open too much. you check with the compressor off of coarse.

Thanks for that idea. I’ll check the gap (should be 0.014-0.026") and if too big, remove the plate and clean it up. On one youtube video he removed a thin washer from a Honda’s compressor shaft and it did the trick - at least in the shop.

On my car it seems to be a heat related issue, so if the above doesn’t work, I’ll look further into that thermal protector: jumper it and see the result. If that works, maybe jumper it and leave it that way.

No solution yet, but I’ll post back with results.

Any other ideas out there?

You might consider that the thermal protector is working, and the compressor is actually running hot.

After all, it is a used compressor you installed.

If you by-pass the thermal protector and the compressor seizes, it can result in black death.


Black death - does that mean debris throughout the system?

I read that low charge is the main cause of a hot compressor - and that a lack of cold air is a symptom of low charge So I am aware of that. If I avoid a low charge condition (or don’t use the AC or defroster in that condition) are my chances pretty good?

If the problem persists after adjusting the air gap, then I’ll have to decide between a new thermal protector or just bypassing it - if jumpering does the trick.

You may have a weak magnetic coil. The next time the clutch fails to engage, bump the drive plate with a screw driver towards the pulley, if the clutch engages, the coil is weak.

Also, if you can reach the coil connector check for power with a test light.

good idea. I forgot I did that before checking the gap.

Others say that can also be a sign of excess clearance. Removing a thin washer fixes it in some cases…but who knows for how long?


The only reason I mentioned to check the air gap was because I had a similar problem on my 2003 f-150. I checked the air gap and it was to much of a gap. I cleaned the rust off the contact points and took out a washer to get the correct gap and have not had a problem since. its easy and free to do. it may or may not be your problem. but it does not hurt to check.

That will be my next step. With luck, my last.

The thermal protector was not the problem. I reduced the airgap by removing a washer; the compressor ran all the time. I did some careful filing of the disc hub and refitting it and its washer. After several such attempts the gap is close to spec (0.020" + or - 0.004") and the AC is working normally again. It took a lot of time. If this does not work reliably, I’ll spring for a new compressor and receiver/dryer.

One more question: if I install a new compressor and receiver/dryer, is it necessary to first have the refrigerant pumped out? Is it necessary to have the system evacuated before putting in new refrigerant? (This system does not use R12.)

Thanks for all the suggestions.

Anytime you open an AC system, any refrigerant in the system must be reclaimed.

And yes. Once the system is reassembled, a vacuum must be applied to remove any air and moisture in the system, and to check for leaks prior to recharging.


glad it worked for you. mine has been working normal for a year now…
and yes, what Tester said.