JeffNReg

'84, bone stock, converted to R134 by previous owner. A/C was blowing hot, so I bypassed low pressure switch and charged. While charging, compressor was rattling like crazy. Now has full charge, blows ice cold but the compressor still rattles like crazy - however, only at idle. If I get the revs up to 1k or higher, rattle goes away. I'm at a loss on this one. Easy diagnosis if the rattle never went away. Any thoughts??

VetteMed

my concern would be, if it was rattling while the charge was low (which means low oil circulation due to low refrigerant), the bearings may be loose or worn out. If it blows cold, I wouldn't worry, but it is possible that the compressor's days are numbered.

Also possible that the wrong lubricant was used, perhaps a higher viscosity oil may be required.

C422

I'm having a similar problem with my '90, though not identical. I heard the rattle from mine and figured it was low on coolant, but checked and the pressure was actually just a smidgen too high. It's started blowing less cool over the past year, too. I wonder if my compressor's days are numbered.

SunCr

Could be as simple as a bad Tensioner, but with an overcharge, it could be slugging liquid and that's going to kill it.

leesvet

I actually have one now that started out rattling horribly...Took it to the place where I bought it and made them listen to it and let them know that it would be back for warranty if it failed anytime soon...they said it shouldn't be a big deal. After about a week it quieted down and now turns quietly and smoothly.

Dons84

I also have an 84 with the same bad vibration at idle. I hope what I have done will help someone solve our problem. Idles about 700 RPM with AC on. Raise Idle 1 or 200 RPM and vibration seems to stop. AC never worked when I bought the car so I replaced compressor and clutch (Proliance from Pep Boys), new ester oil, new orifice tube, new drier, new belt, evacuated system, installed correct amount R134 and it vibrated after startup. After a week went by I pulled compressor and PEP Boys exchanged it. I reinstalled but unfortunately same vibration. I am assuming two compressors cant be bad. Other than the vibration AC works great and blows plenty of cold air. Its been three years now and have learned to live with vibration I shut AC down at stop lights. I have been watching this forum for some one with the same problem and hopfully a fix that I have overlooked. Thanks.

SunCr

I bought new from Autozone ONCE - squealed like a goosed pig the minute I started it. Drove to Autozone and had the Manager listen to it. Got another one; plus the gas I wasted (probably should have insisted on another Accumulator too) and started over. It was fine after that. The guys that do this for a living swear that the Discounters foist off repainted cases with maybe a new clutch as new stuff.

Drain whatever oil is in the replacement and flush it with whatever you're going to use by dumping in 4 ozs and turning the shaft a dozen or so times in one direction; then the other. Dump and repeat and leave 4 ozs in it to ensure enough lube when you start it up.

Rattles, vibrations, noises, etc aren't normal and they didn't leave the Factory that way. Make sure all the parts; ie, brackets and for those years that use one, the doughnut or frisbee on the front of the waterpump are installed. Remove the belt and spin the Pulley slowly. There shouldn't be any roughness or any signs that it's out of round. Crank the shaft by hand. It should turn over with minimal resistance. Make sure you've got the right belt - '89 had the wrong size in the Goodyear Catalog and the couple of mm's in extra length caused a noise. Make sure the Tensioner is within the alignment marks. Check charge - particularly with a conversion. There's been some gross overcharges posted around here with the Low Side hitting 60 psi which means 70 to 75 degree air. Scan it to check Actual vs. Target Idle. If Actual isn't within 100 rpms of Target in Park/Neutral or 50 in Drive, the ECM isn't handling the Load which is usually too much juice or a bad compressor though there could be an engine management problem. Also check a/c request and clutch engagement. You'll probably feel it up until '90 when the PCM took over clutch engagement, but it shouldn't be a big lurch and IAC counts, pulse width should increase with a "Yes" in the a/c request. If any of those things are out of kilter, it's usually the ECM but you should check the a/c request voltage at the ECM pin first to rule out a wiring or Dash Control issue.

barmitch

Ok I know this is an old thread but this rattle at idle in the AC is a common one. So here it what you do is dismount the AC compressor but just to lift it up a bit. The issue on many cars is that there is a spacer missing on the bottom bolt at the rear. What happens is that the sleeve that goes through the mounting bracket is tightened and then the sleeve digs into the soft aluminum of the compressor and it comes loose. With out the spacer it bounces around and make a hellish racket at idle. This rattle goes away when you raise the RPM a couple of hundred or so. Here is what I did: I drilled the body of the AC so I could fit a sleeve in there on each end now only about 3/8 deep however and I used a 1/2 inch drill. Got the sleeve to go in there from a hardware store and I just cut it so that it was flush with the outside of the case of the AC body(easier to fit and then grind with a dremel so that it is flush.) These sleeves make sure the bolt is supported at each end. Next you remount the AC and hang it from the top tensioner bolt as it makes it easier and snug this up so that it holds the AC unit about where the lower mounting bolt is going to go. Now look carefully at the rear lower mounting bolt and see if you can. see a gap between the AC and the bracket. If you can see a gap this is the problem! Now take a thick washer and grind it down till it will fit snugly in to the gap.This washer should be steel..There is also a sleeve going through the rear mount hole in the bracket which can be left or cut down till it fits the depth of the bracket. I left mine and just smoothed the damaged edges and squared them up in the grinder . Put blue lock tight on the lower mounting bolt end, slide the bolt in (put the spacer in) and tighten but not too much. Tension the belt and tighten the nut. Then tighten the lower bolt. Hey presto there is no more noise at idle. There was a bulletin on this from Chevy and the part number for the spacer sleeve (replaces the washer)and is fed in from the in side of the lower bracket but I couldn't find it any where so I made the spacer. Here is the part number P/N 3976216. This was an issue with the 1978 corvette but I had the same problem on my 81. Bulletin number 78-T-76. So good luck and I now have a sweet quite AC at idle.

The second thing that causes this rattle if the A/C is good are loose bolts on the brackets. Lastly, and this is common also, is that there is a protective plate over the lower radiator hose. If this is too high the A/C belt will hit it and it makes an awful rattle, high metal rattle sound, at idle. When you speed up 200 RPM it goes away. So what you do is bend it down away from the belt (quite away down) as it is there to protect the radiator hose in the event of a belt break. Bend it down...no more rattle...but also check the belt tension on the lower part of the belt.

There it is...