intermittent a/c compressor clutch (flaky WAC)?

[austin-tatious]

A month ago the a/c quit working on an intermittent basis, and it's obviously something to do with the a/c compressor clutch. When it quits, the clutch is not engaged, so the compressor doesn't compress, so you get no cold air.

So the dealer keeps it for two days and cannot reproduce the problem. Figures.

Forturnately (or unfortunately if you want cold air) it seems to be happening more often, so resolution of one kind or another should be close.

I'm suspecting the wide open throttle a/c controller or WAC. That is what disengages the a/c compressor clutch when I mash it to the floor (which I like to do alot). But there are no DTCs either from the PCM or from the EATC.

I have the manual on DVD, but there is no procedure listed for RR the WAC, and for some unknown reason I cannot view the wiring diagrams...probably due to using this ancient W98 333 MHz system.

Anyone know where the WAC is located?

Mine is SergntMac's original fastest NA in NA. Well, it was at one time. :)

[SergntMac]

Hey Bob, nice to hear from you again, hope you and Sharyn are well.

I can't help with your issues, the HVAC is a mystery to me. But, I wonder if there is any belt slip under WOT?

[TooManyFords]

You should also have the system checked for a slow leak. The clutch will cycle on and off under low charge as a safety method to keep from ruining the compressor.

John

[JMan]

There is no WOT switch. The PCM uses the throttle position sensor for determining WOT. Also not likely to be low refrigerant because when it does work, it is cooling. The dealership or repair center needs to see it when it's failing to determine where the issue is. It's a crap-shoot otherwise.

Most repair shops should be able to command the compressor on and off independent of the A/C controller with a quality scan tool. It might pay you to unplug the compressor and check/clean the contacts on the plug. That used to be a problem on the older Ford products. Yeah, I know it's in a miserable spot to get at!

Best luck,

J

[Marauderjack]

Take out the bolt that holds the clutch together and remove one shim to close the gap on the clutch.....If there is only one shim find a thinner washer and put it in and it will work fine...just be sure you have about .005" gap and you will be good to go .....Don't ask me how I know!!!!:argue: :mad2: $35.00 education and it works on all Ford products!!:beer: !!

Good Luck!!:rolleyes:

Marauderjack:burnout:

[austin-tatious]

Hey Bob, nice to hear from you again, hope you and Sharyn are well.

I can't help with your issues, the HVAC is a mystery to me. But, I wonder if there is any belt slip under WOT?

Thanks Sergnt, we're fine except for being a little warm when the compressor decides to not compress. But we're having an unusually cool May, so we're wont to roll the windows down anyway. However, June is coming...

The dealer did check everything. Belt's fine, coolant's fine, etc., etc. But, since it refused to fail while there, he gave up. The problem is it just turns off. You can stop the car, open the hood, and see the compressor not compressing.

[austin-tatious]

There is no WOT switch. The PCM uses the throttle position sensor for determining WOT. Also not likely to be low refrigerant because when it does work, it is cooling. The dealership or repair center needs to see it when it's failing to determine where the issue is. It's a crap-shoot otherwise.

Most repair shops should be able to command the compressor on and off independent of the A/C controller with a quality scan tool. It might pay you to unplug the compressor and check/clean the contacts on the plug. That used to be a problem on the older Ford products. Yeah, I know it's in a miserable spot to get at!

Best luck,

J


Take out the bolt that holds the clutch together and remove one shim to close the gap on the clutch.....If there is only one shim find a thinner washer and put it in and it will work fine...just be sure you have about .005" gap and you will be good to go .....Don't ask me how I know!!!!:argue: :mad2: $35.00 education and it works on all Ford products!!:beer: !!

Marauderjack

Thanks for the ideas. I hope one of 'em works.

BTW, I reinstalled the DVD on my not quite so old W2K system, and now I can see the wiring diagrams. Seems the W98 system did not allow installing the adobe svg viewer that is required.:cool:

[austin-tatious]

Update: 1. Checked the wiring connection at the compressor. It's ok.
2. Did not reduce clutch shims since I need a special tool to hold the clutch while I unscrew the bolt...too lazy to fabricate one.
3. Proved beyond a doubt that it's somehow related to WOT and the WAC. When it quits working, as soon as I (or mrs tatious) goes WOT for a few seconds (which may not be possible for a little while) and then back off, the clutch kicks in and we're cool once more. This happens whether I have the stock tune or the SCT tune in the computer.
4. Talked to Dennis Reinhart on the phone about it. He suspects a heat related problem with the compressor clutch coil. When it quits, I should be able to pull the wiring connection to the compressor and see if there is 12V or not. If there is 12V, then the clutch itself is flaky. But how does that relate to going WOT to get it back on????

[Marauderjack]

I have done the shim thing on 3 or 4 CV's and unless they have changed things you can hold the clutch with your hand....Only about 15 Ft Lbs on the bolt??:shake:

If you have more tha about .005" clearance with the clutch disengaged the symtoms you describe will be cured by reducing the gap!!:beer: I didn't believe it the first time but after several cases....I BELIEVE!!:eek:

Marauderjack:D

[austin-tatious]

I have done the shim thing on 3 or 4 CV's and unless they have changed things you can hold the clutch with your hand....Only about 15 Ft Lbs on the bolt??:shake:

If you have more tha about .005" clearance with the clutch disengaged the symtoms you describe will be cured by reducing the gap!!:beer: I didn't believe it the first time but after several cases....I BELIEVE!!:eek:

Marauderjack:D

Thanks to this advise, I have almost eliminated the problem. The gap was about 0.032" and there was one shim measureing 0.035". The shim kit Ford sells does not have anything smaller than 0.0275". So I began filing the shim down. When I had the gap at about 0.015", the intermittent was less frequent but still there. More filing got it to 0.012" plus/minus 0.001". That gives a gap of about 0.009". Still too big according to Marauderjack, but the failure is very rare now.

I have also noticed that the cold output is more intense with the smaller gap (except when it quits, of course). That makes me think there is something to the idea the clutch coil has become much weaker, and might fail altogether before long. That would be because a weaker clutch coil with a larger gap would allow slippage, but with the smaller gap the coil has less distance to pull the clutch tight, and therefore slips less or not at all so the compressor does a better job.

I'm considering replacing the clutch anyway, and set the gap as I have it now.

I've also noticed that

[SMOKE]

I know the clutch on mine is sorta wierd. A Ford friend pointed out that mine "chirps" as the clutch cycles through engage/disengage like his Mustang did and also an Explorer his wife drove (both about the same year as my MM).

Got cold air and a chirp I would have never noticed until my buddy pointed it out (now I notice it ALL THE TIME:argh: ), so I'll take what I have. I think he fixed his 'Stang compressor with the shim trick and a new belt (thought their might be slippage).

JWM

[kj31067]

mine does the chirp too , but works flawlessly and is cold as a bastid.:D

[austin-tatious]

Finally, the a/c is back for good.

Since I last reported on this, the a/c going off (usually when we needed it the most) just got worse and worse. On a trip from austin to dfw, it would stay on for maybe 10 to 20 min max, then cut out. We had previously discovered that a quick part throttle rev to 2,000 rpm over whatever the current rpm was could kick it back on most of the time.

After that trip I decided to give my mechanic a chance at it. They found it was almost a pound low on r134 and we all thought that was the problem. The same day I picked it up, it quit again after about 10 miles FOR GOOD. No more intermittent, no nothing.

Back to the shop, and they diagnosed the clutch coil was not working. Then the next day I get a call after they got it apart. The clutch coil bearing shell was actually broken! And there was evidence of coolant leak around the compressor shaft. Now it's a complete compressor and associated parts replacement plus recharge job.

Fix is done. Air is cold...all the time. I've got that bearing for a souvenier.