A/C Compressor - Please help diagnose (lots of details for experts)

[BruthaMan]

Guys, I need some help diagnosing an ac compressor issue. Please bear with the information below. Trying to make sure I document what I've done, so those with experience on this have as much information to determine a cause and possible solution.

Some background:

I have read, read and read for weeks (in spare time), posts from this forum and other auto-ac sites. I have absorbed information and learned (which was my goal...I make good money, the decision to learn this was not one from saving money, but rather a desire to learn) a great deal about AC systems that were for years, a big mystery to me.

When I bought my 72 a few months ago, the previous owner mentioned that the compressor on the truck was new. It has the black metal seal over the ports in the back. I'm sure that it was a new compressor.

I ordered a new hose kit, and all new hoses, including the aluminum hoses from the condensor and dryer. I flushed the entire system, thoroughly, multiple times as it had been open for an untold amount of time when I bought the truck. I have installed a new condensor, new dryer, new expansion valve, new AC Switch, relay and high speed resistor (since we gutted the entire truck AC system to clean out 40 years of dirt, leaves and debris). Pretty much everything is new except for the evaporator core (which was fine, though we cleaned it good) and the POA valve.

I removed the POA valve, cleaned it good (flushed it) and built a POA valve tester, hooked it up to the tester with 60 lbs from the compressor in my garage, and adjusted the POA valve to 29.5 PSI (per instructions on the autoacforum.com).

In short, I have meticulously prepared for this. I have all the tools and I've probably taken more time than most would because I really want to learn this and make sure I do everything correctly.

First Attempt:

With the first attempt, I tried out Auto Refrigerants ES-12a. I used Ester oil on this attempt. We got it to cool some, down to about 58 degrees at the evaporator core (using a digital temp gun). I was concerned about pressures at that point (using a gauge set on high/low side to monitor pressure).

Up to a point, the compressor was fine. I took it one can more and suddenly the compressor started squealing. Not the belt, the compressor. And it would start "locking up" some, where it was struggling to turn.

At this point, after doing some reading, I thought maybe the clutch had given out. So I replaced the clutch.

Second Attempt:

Next, I flushed the system entirely again, thoroughly. I flushed the compressor, thoroughly, in preparation to use mineral oil (used 11oz of mineral oil). I came across a large stash of r12 cans locally and figured why not use what the system was meant for. I bought another new drier since I previously used ES-12a. Figured it was a safe bet for going to R12.

Pulled vacuum for 45 minutes, let site for about four hours, no leaks. Started adding r12. Engaged system, started seeing the compressor squeal again when A/C was engaged. At this point I figured it had to be the compressor that was bad.

So I found an NOS AC/Delco compressor for our trucks on Ebay. Great score. It was minus the clutch (original box and instructions) and I just happened to have a new clutch that was put on the previous compressor and used for maybe five minutes.

Third Attempt:

Uninstalled the new clutch from the old compressor and installed it on the new AC/Delco compressor. I drained the oil from the compressor. I wanted to be sure it had the correct amount of oil in it. Added 8oz of mineral oil to the compressor and 3 oz of oil to the drier.

Pulled vacuum for 1.5 hours. My home AC guy was at the house today and said it wouldn't hurt to pull vacuum for longer. Also recommended to pierce the cans first, let a little start coming through, THEN hook up to low side on POA valve so no air would get into the system.

I picked up all new belts from Napa. Figured we were here, might as well replace all the belts. We replaced them all. Snug, not too tight. These are the good belts.

So, after four hours to make sure there were no leaks, we started off by adding one can of r12 to the system. Next, we started up truck, put fan on high, engaged AC.

The heart of the issue:

SQUEAL!!! It's now doing the exact same thing as before. The compressor is squealing the instant the AC is switched on. It acts as if the compressor is just not able to turn. The belt is tight enough, but not "too" tight.

I'm at a loss. How does the same symptom occur with two different compressors and two different clutches (I don't believe the old clutch was bad)?

The belt is on the right pulley, it looks straight when looking at it from the side.

We hooked up a voltmeter to the A/C power pigtail. Was getting 11.5 to 11.7 volts when it engaged.

Is there anything else I could be missing? I've spent a good month on this, between waiting for parts to get here, trial and error, etc. It's like everything is perfect, except that the compressor is squealing and not wanting to rotate.

I should mention also, there is no problem when the A/C is NOT engaged. Belt/pulley turn fine, not issue. Only when the A/C is engaged.

A brutha's gotta have his A/C. I don't do well in the heat and I live 10 miles from hell.

Recommendations?

[Low Elco]

My experience has been that on a v-belt system the ac belt especially needed to be Hulk Hogan tight. Might also consider cleaning the belt track in the pulley with lacquer thinner/brake kleen and 80 grit paper, I've had that help. I am no expert and will be converting the 87 over to serpentine. I hate v-belts with a passion. Sorry you got caught in a hair-ripper, Bman. Sad part is, that stuff is so bygone, even the techs at a ac specialty shop will probably blank stare ya. Hope you get it goin.

[VA72C10]

moved for you....sounds like you've done your due dilligence +some....hope someone has an answer....I'll agree on tightening the belts and cleaning them but you're saying this is coming from the comp itself??? are you 100% it's not belt squeal?

[Andy4639]

Well if it is the compressor you only have 2 things to look at. The compressor shouldn't squeal if it's low are high on freon.

The belt being the first thing to look at. The V-belt needs to be as tight as you can get it and then some. I even put a extra bracket on the compressor to help hold it in place once I tightened the bolts up.



The only other thing is the clutch itself could be bad. New parts don't mean they work the way they should.

[JimKshortstep4x4]

BruthaMan,

It was interesting to read your write up on the AC problem. I believe that you have the assembly and the system figured out and what you wrote will be a help to others.

The belt as mentioned has to be really tight and the quality of the belt is very important. Once the belt has slipped for any length of time it is almost impossible to get it tight enough to drive the compressor so replacement is needed.

Good luck!

Jim

[GMC Canuck]

what is squealing? Is it the belt slipping or the clutch itself slipping?
can you turn the compressor over by hand? It should be a little stiff if there is refrigerant in the system or turn real easy if the system is empty.
What did you flush with? Is it possible there was some flush trapped in the system? Some of the commercial ones are pretty nasty and if there is any left in the system it will thin out or wash out the compressor oil.

[ole dollor]

bruthaman: have you tried running a jumper wire from the battery to the compressor , to give it a full 12 volts , just to see if it still squeals , if its not the belt , see how easy the compressor turns by hand , say about 15 or 20 rounds, if the belt is off you can do this with a socket, with the belt on turn the clutch off, see what it does both ways, belt on clutch off, belt off clutch on , and off, hope this helps.....good luck....

[bollybib]

A lot of good info here. Eventually I want to restore my AC and this will be useful. Thanks to all who posted.

[BruthaMan]

Thank you, gentlemen and an extra thank you to VA for moving the thread up into the main area. I originally posted down in the build area. Not sure why, didn't even realize I was there when I posted. I plead "temporary loss of cabin pressure!"

I got as far as loosening up the front and rear AC bracket this morning, sanding down the pulley with some eighty grit and using "grease and wax remover" on the pulley and the belt, before "Grandpa Daycare" kicked in for the day. Three of our grandkids are staying with us till next Friday (one pretty much lives with us full time). Two are five, one is seven. And two others stopped by for a few hours this afternoon. Love them all, but man is it chaotic here!

Reading through the responses, I'm starting to think I don't have the AC belt tight enough. To further explain this, when the compressor kicks on, it's wanting to turn and does turn some, but you hear the squeal and can see *at the point of squeal* that the compressor/clutch is not turning. So that would indicate the belt is the squeal source, because it's slipping on the pulley/clutch.

There is R12 in the system right now, though not fully charged. I can *barely* turn the clutch some, by hand (not the pulley, but the clutch). I'll put a socket on it this evening, if I can catch a break.

The belt is brand new. It's only been run for about two minutes, when we were turning the A/C on/off. It is much thicker than the previous belt that I had on.

I also picked up some belt dressing.

My plans this evening are:

1) Clean the belt one more time with grease and wax remover, to make sure there is no oil and the pulley groove as well.

2) Spray some belt dressing on the belt.

3) Put the belt back on, use a pry bar (probably get my son or neighbor to help with this) and *really* tighten it down. It was not very tight, as I was afraid of over-tightening it. It was "snug" but not too tight.

Question was asked on what was used to flush with. The first time I flushed the system, I used A/C Pro flush from O'Reilly's. The system was apart and I flushed everything individually, into a bucket to catch the flush. I then used my air compressor, set at 60 lbs on the gauge, with a rubber tipped air sprayer to spray out residue.

That flush is pretty expensive. I used three large cans of it.

On the second second attempt, when moving from ES-12a over to R12, everything was disassembled again. I used Acetone in a harbor freight "hand held sand blaster" to spray through parts. I realize that's going to sound weird, so I'll explain:

I wanted something to "force" the Acetone through the parts. I went up to HF and saw the little "hand held" sand blaster. I had used one of those before for light sand blasting, so I bought a new one and added the Acetone to the cup, hooked up the air hose and sprayed it through the system. It actually works pretty well and was the only thing I could find, where I could spray the flush through the system with some volume.

I then used the air tip with rubber end to spray air through all the parts to get any final residue out.

It was cleaned out/flushed pretty well because I used Ester oil with the ES-12a on the first attempt, and I wanted to make absolutely certain the system was well flushed for moving over to the mineral AC oil (picked up at our local Napa).

Back when we still had that first compressor on, I did hook up a direct wire from the battery to the positive on the AC compressor, but there was no difference. I have not done that test with the new AC/Delco compressor on.

Reading through the responses, I'm really inclined to believe I just didn't have the belt tight enough (and this comes from my inexperience here.)

I will follow up once I'm able to break free. Kids are laying down for a nap now, so I may head out to the garage and see if I can get a the last few steps done and try again.

It's good to have everyone peeking over my shoulder! I appreciate the advice!

[Low Elco]

You Sir, are a far more thorough and patient soul than I. Good luck!
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[JimKshortstep4x4]

I have had some really bad experiences with belt dressing in the past. Used car lots used it to quieten belts but the effect only lasted a short time. My suggestion would be to try tightening the belt without using any dressing on it.

I have not used it since!

Jim

[chebyshortbox65]

What are is the pressures in the system while a/c is running?if the compressor is locking up and the belt not slipping then you have to much pressure on the high side it will destroy the compressor quickly.where are you adding the r12?you have to add it to the low side while the aystem is running.also the pia valve is junk most people buy the kit to get rid of it just my .02
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[sneakysnake]

Sounds like your head pressure is to high,if the expantion valve is not opening properly it can cause this. Should be about 40 on low with around 250 on the high.You never mention your pressures so its hard to tell exactly whats happening.

[BruthaMan]

Wanted to update this thread on progress in case it may help someone else down the road.

We tightened up the belt, using a "man bar" (big pipe) for leverage. Added some belt dressing as well, just in case.

This stopped the maddening squealing.

I did add one more can of r12. Low side was at 30psi, high side was right at 205. This was in 90-95 degree ambient heat, with truck at 1500 idle.

Things started to cool, then started to heat up again. I have a heater shut-off valve (new), hooked up, but for some reason it was not engaging to prevent hot water into the core, so we were getting a mixture of cold/heat and the heat was winning.

To further hinder progress, once idle was back at normal, the squealing started again. I looked at the pressure, and the low side shot up to about 65, which isn't good. We were using hand signals and I gave the sign to cut off the AC immediately.

I'm thinking that I'm introducing air into the system when I'm adding the R12 and this is causing the compressor to struggle and squawk and variation in the pressures.

Since everything is together and there are no leaks, I think at this point I'm going to take it to a shop and have them pull a vacuum and add in the R12.

I'm not one to easily give into defeat, and I've learned a lot, but this is really the last step for the truck to be on the road (I've already been driving it some).

I appreciate everyone's advice and support.

[GMC Canuck]

good find on the water valve. Any time the heater and A/C try and fight each other, the a/c always loses. The low side shooting up to 65 isn't a major concern, it could be just the belt/clutch slipping so the compressor stops pumping. Did you happen to notice the discharge pressure when this was happening? I would watch your discharge pressure. over 200 is getting a little high but with 95 degree ambient not abnormal. If you have air in the system your discharge pressure will be really high.

I would be careful using compressed air to flush a system. Make sure you have some sort of drier or water separator on your compressor. Water even in small amounts can cause large problems. If there is water in the system some time on a vacuum pump will boil/evaporate it out of the system but it does take quite a while. Same goes with most commercial flushes, it should evaporate.

[ChevLoRay]

I know the original system used R12. Now the question: did any of the accompanying paperwork mention which type of refrigerant to use? I know you said you bought an NOS compressor, which logic says should use R12. But, do the aftermarket/reman compressors, even OEM types, require R12, R134a or Freeze-12? I haven't done any research, just wondered.

[Low Elco]

Not to belabor a point, but ensure a good tight shut seal in the hot cold flapper door. Mine wasn't on my 87.
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