Swapping the Clutch on an R4 A/C Compressor

[PlayingWithTBI]

The other day when I was waiting for curb side delivery at Total Wine my A/C started blowing warmer to the point it was cooler than the vent but not cool enough to keep me from sweating. It got a little cooler when driving home on the freeway then, when I got off at my exit it started blowing cold again. I'm thinking the clutch may have been slipping? Yesterday I put my gauges on it and started the engine up. I was getting ~45 on the low side and ~150 on the high side - pretty low for ~100* ambient. When I revved up the engine the low side went down to ~35 then started surging back and forth between 35 and 40. The high side didn't go up hardly at all. This weekend, I'm gonna pull the clutch and inspect it maybe swap it out. I have a spare compressor I put together out of 2 others - 1 which blew the high pressure switch out of it when I didn't have it wired in series with my low pressure "cycling switch" (my 88 didn't come out of the factory with a HP switch). The other compressor was an almost new one from NAPA that had the air gap on the clutch too big and smoked the clutch in a couple days. So I put the clutch from the 1st one on the 2nd. Anyway, I couldn't remember if you can remove the clutch, pulley, and coil without bleeding the system, you can! I'm documenting this in case anyone is interested on how to do it.

Here's it all apart with other tools you'll need.

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1st - remove the 3/8" NF nut (9/16" socket) on the shaft using an impact driver. Then, using the clutch removal tool pull the outer plate off. There's 2 ways to do it, with 3 bolts and the hub or, with the removal bolt in the center. Some R4s come with metric threads and some come with SAE. In this case they're SAE so, I used #8-32 bolts.

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Here's the other way of doing it - mocked up.

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Remove the external snap ring which holds the inner clutch and coil in place.

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Then remove the inner clutch plate/pulley with a puller.

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Then do the same on the coil. Note: the bearing in that pulley is installed at the factory and then the housing is peened to hold it in place - not really a user friendly replacement.

I'll post what we find when we tear into the one in my truck. Hopefully I'll have enough room once I remove the top 1/2 of the fan shroud.

 

[someotherguy]

An important take-away from this is the incorrect air gap on the new NAPA compressor. I've never thought to check one from an out-of-the-box unit, usually only when a compressor gets older and the clutch stops engaging reliably. Usually once we notice though it's too late.

Richard

 

[PlayingWithTBI]

Yes, it was over 0.080" where it should have been 0.020" - 0.030". And the air gap is adjusted by pressing the clutch further in, it doesn't have shims. I'm gonna add a washer or 2 and adjust it down with the 3/8" Stover nut to get my gap. Maybe some Locktite too?

 

[someotherguy]

If you think it needs it, probably some blue Loc-Tite so you can remove it later easily if need be. I haven't had one come loose once set, on both A/C compressors and hydraulic pumps. YMMV

Richard

 

[PlayingWithTBI]

Yeah, I just hate doing things twice and, this bast*rd is on its 3rd replacement compressor and 4th time since I rebuilt the system. Everything else is good to go.

 

[Schurkey]

Why are you suspecting the clutch is slipping, when the high-side pressure is so low? There'd be minimal stress on it since it's not doing much "compressing". If the clutch can't handle idle speed, I wouldn't expect it to do better when the engine is trying to drive it even faster.

Your high side pressure is abysmal. So, yes, you could have compressor problems. Slipping clutch is not the first thing that comes to mind.

I would have added some refrigerant and seen what happened.

 

[PlayingWithTBI]

Why are you suspecting the clutch is slipping, when the high-side pressure is so low?

Because, when I rev it up it doesn't suck down the low side (it just wavers between 35 & 40 IIRC) or increase pressure on the high side. If it was low on freon, it would suck it down below 25PSI and the clutch would release due to the cycling switch. It's still blowing cold but, I didn't put a thermometer on it to confirm it was blowing as cold as it should.

So, yes, you could have compressor problems. Slipping clutch is not the first thing that comes to mind.

I should be able to look at the clutch for signs of over heating or damage before opening the system to inspect the orifice tube for pieces and parts. I don't have a reclamation system and don't want to loose all the Freon if I can help it.

The confusing part is driving home on the freeway blowing semi-hot air then when slowing down on the off ramp it started blowing cold again. That leads me to thinking the clutch is slipping. I'm going to ohm out the coil and compare it to my spare one too.

 

[Erin]

I had same problem with blowing hot on interstate and then cold when I slowed down. My clutch was seizing up. Whine and grinding like crazy. It was only 6 months old.

 

[Insert Quarter]

Yes, it was over 0.080" where it should have been 0.020" - 0.030". And the air gap is adjusted by pressing the clutch further in, it doesn't have shims. I'm gonna add a washer or 2 and adjust it down with the 3/8" Stover nut to get my gap. Maybe some Locktite too?

I've had good luck with Permatex Orange 25210

 

[PlayingWithTBI]

My clutch was seizing up. Whine and grinding like crazy. It was only 6 months old.

Mine's quiet and the air gap is still ~0.020". It's not very old either.