91 B2600i, a/c working now....strange....

Again: check first to see if the issue is that the AC clutch is slipping, that the magnet is pulling the hub in to engage, but that either the gap is too large to keep it engaged completely (like from the loose nut) or possibly oil that got onto the AC clutch surface.

Yes, I did use aerosol brake cleaner to clean off my own slipping AC clutch, but I was careful NOT to spray in where the AC clutch bearing is, only on the interface which should be locking up.

I doubt that things have worn to where a washer must be removed or replaced with a thinner one to make it engage, but this stuff has happened. In this case rapping on the center (be very careful of belts and rotating stuff here) will cause it to become engaged, and it should hold that without slipping if a too-large gap is the only issue.

So first step is to determine whether the issue is slippage, or failure to engage. When my own B2200 experienced same, was evident only at idle, and was clutch slippage, as described above.

I guess Im not sure what is causing the compressor to disengage. I have seen what I think is 'slipping'......clutch looking like it was trying to spin with the belt, but turning very slowly, until i beat on it and 'freed' it up? Not sure though if that's happening while im driving though. Def feel it disengage, air becomes hot and rpm's go up, telling me the compressor has stopped working......but again, not sure if it is the clutch causing that to happen. I think ive eliminated the possibility of an electrical issue causing it, with the exception of this pressure cycle switch that was mentioned earlier. It has been converted to R-134, and the last time I had truck in shop, was told pressure was right where it needed to be, so I dont think under/over charge is the problem.

Which leads me back to the clutch. I have witnessed numerous times the clutch appearing to be 'slipping', trying to spin but unable to until I tapped it. I had an issue with coolant spewing from a hose a couple weeks back, so I think it's possible some fluids may have gotten into the compressor/clutch. And I havent checked the tightness of the nut either. Although, as I think about it, something does look 'off' when the clutch does engage and is spinning. maybe a slight wobble.....or the appearance of something being bent?

Sure sounds to me like the AC clutch is getting power, and that sometimes there is a failure of the clutch to engage or "catch", because you can tap on it and get it to engage. So I'd start there, and fix what you KNOW is bad first: that slippage. If my feeble memory serves, that nut is a 17mm socket to tighten it. With engine off and ignition and AC on, get the clutch to engage by tapping on it, and the belt should hold it so you can tighten the nut. I will report that the loaner clutch holder tool I borrowed from AutoZone a few years ago (when I had my similar issue) was not the right size to hold it steady.

When similar happened last year to me, I checked and the clutch nut was still tight, and observed a little oil on the AC clutch, so I used brake cleaner aerosol to clean that off. I actually think the AC has worked better on mine this year than in the past, I switch it off and on on my way home, and it's been over 113F here for most of the past few weeks.

Thankyou again for the replies to this. I'll try the method you described to tighten that nut down. Too dark now, but tomorrow for sure. Seem to be getting closer to finding the problem.

I think you are getting closer to finding this out.

I sure can't ask you to drive to Phoenix without AC in this heat so I can take a look !!! Plus, that travel would end up costing you more than having a dedicated auto AC mechanic to look at it.

So question....I did manage to engage the compressor clutch with the engine off as described and attempted to tighten the big nut in the center. I dont know if this is normal, but the entire clutch or shaft of the compressor spun with it as i tried tightening it. Not loosely, but with the torque i was applying, it was spinning the entire assembly around it slowly.

I was reading about the 'air gap' possibly being too big, and causing the magnet not to have enough strength to pull the two sides together, which might also be causing this intermittent non-engagement of the clutch. I also read there should be washers or spacers that can be removed to close the gap.

How does one remove that plate on the front of the clutch to gain access to those spacers? Since everything seemed to spin while i was trying to tighten that nut, i assume i would have to hold the plate in place while loosening that nut? Special tool?

again, thanks for all the help!

Hmmm - what you describe above - is the compressor turning but not the engine (I'm assuming that the truck is in neutral, though) ??? If so, how's that AC belt tightness ??? See, I was assuming that the belt would prevent the compressor from turning if engaged, but that depends on the AC belt being tight. You're not just having belt slippage when the compressor engages, are you?

OK, how does one even access such washers? First, the compressor must be held stationary (by a tool or by having tight belt and engaging the compressor), then the nut unscrewed. I know I had to rig up my own tool to extract the compressor clutch, the loaner from AutoZone wouldn't fit. If need be, I can dig out that tool I made on Saturday, and get photos up.

I followed the steps outlined in your previous posts, turned ac to on and ignition on to get clutch to engage. Attempted to tighten the nut on compressor, but it caused the assembly to spin with it....i dont know if that means it's already tight enough? Belt seems to be tight enough, there is a little play, but not too much. It bends when I push it with finger.