I turned the A/C on for the first time today, and when the car is at 800 rpm, there is a vibrating/grinding noise coming from the compressor. You know that sound if you have an exhaust clamp vibrating on something, the wound is similar to that. It sounds like somebody stuck a piece of tin in a fan blade that is turning, and is very loud. If the motor revs below 800, the sound goes away. If the motor revs above 800, the sound decreases in loudness and intensity until 900 and then goes away. It sounds more like it is coming from behind the pulley. I know the bearing would be the obvious culprit, but if the bearing is bad, wouldn't it do that throughout the rpm range? There is no noise unless the A/C is engaged. Could it be such a thing as the clutch is not engaging, disengaging all the way? Is there something behind there that can come loose and vibrate? Aside from the noise, the A/C works fine. Somebody help me please, it's 90 degrees outside, and is suppose to be hot for the next few days.

Also, I just got an idea and went out and checked. The compressor does not appear to be cycling; the clutch seems to be stuck in the engaged position. I sat in the car for about 2-3 minutes, and not once did it disengage.



Eric

 

Those compressors are typtcally noisy. Mine is a little noisy too but is sounds like you may have a bad clutch. That can be replaced without having to change the whole compressor. Have someone check your Hi and Lo side pressures and check all the bolts that hold it in incliding all the ones on the big bracket. If you have taken your AIR pump off you will need to get a bolt and make a spacer that will fit in the top hole that used to hold the pump on. Tighten them all up good. If it blows real cold and then the airflow seems to slow down you may be low on freon and your evaporator coil is freezing up. The low pressure could cause it to run non stop too.

 

Mine is doing the EXACT thing! Funny thing is that I have removed the airpump and the instructions said nothing about a spacer.

If the clutch can be replaced w/out removing the compressor, is there any online instructions on how to do this. There is nothing about the A/C that I could find in my Haynes manual.

Thanks!

 

I wouldnt change anything out unless its not working. Mine has been a little noisy for over a year and blows ice cold. I did however greatly reduce the noise level by putting the AIR pump bolts back with the spacers in and tightening it down. That made a huge difference. My local AC guy also told me that those H4 compressors are notoriously chattery. Might want to check the freon level if you retrofitted over to 134a. It takes less 134a than it would R12 to fill the system. ( I cant remember the exact calculation). If you can get ahold of a set of gauges charge the low side to 38-40 psi at just above idle and youll be just about right.

If you still want to change out the clutch there is a bolt in the center. Just take that off and use a puller (three legs ans a bolt in the center) and pull it off. You shouldnt have to discharge the system to do that.

 

This is a 85, so it's V-belts?

My 83 has done that for as long as I've had it. The pulsation of the compressor seems to stretch and unstretch the belt, and that's what the vibe is in mine anyway.

You could try a new belt; make sure it's tight, and that all the brackets are there and that their bolts are tight.

 

Mine is an S-belt. Tensioner still shows tight. It didn't do it before I pulled the motor apart, but it was sitting for awhile. I watch it and the s-belt is vibrating all over the place while the noise occurs. System is r-12 as far as I can tell (bought the car 1 year ago - Ive never changed a thing and no label shange on compressor). I'll try the spacer though and re-torque all bolts since it's pretty easy (and won't cost anything). See what happens. Sorry if I've hijacked the thread, pls carry on.

 

No prob, pretty old thread but thats what its here for. I wish there was an AIR delete puly as I did see vibration on the long streth between the AC and the balancer. As far as the V-belts go, It might still be the same thing if the AIR pump is off. Just the vibration being able to resonate through the loose bracket. Not totally sure on that one but its wor the shot. If you have to buy new bolts and bushings its stil under $5. Worth the shot.

 

RB,

Does your '83 have the add-in compressor brace? I vaguely recall seeing a TSB on the earlier ThirdGens for AC compressor shudder at low RPM. The factory fix was to install a tubular, tangental brace from the exhaust manifold stud at cylinder 3 to the rear edge of the upper compressor mounting bracket. As of 1985 or 1986, this was a standard item from the assembly line.

 

It'd look a l'il bit like this:

 

No, I don't have that. I do have all the other ones on it, including the one from the intake. Maybe I should keep my eyes open for one; or just make something.

 

COOL, another reason to surf the junkyard. Ill see if I can find something, If so Ill let you know and shoot it to you. It does look like there could be another brace on the outside of it.

 

I had the extra brace before, but had taken it off because it interfered with the headers (no passthough to the block). Guess I'll have to dig out the drill this weekend.

 

Check with a weld shop or metal gate fabricator. They may be able to bend some iron stock to fit relatively cheap. Id still get the pressure checked, It might me low causing that noise from not enough head pressure.

 

Once I do the low-buck stuff, I'll have it checked - it blows quite cold, so I didn't think there would be a problem with the pressure. I still have the bars for the a/c (and the alternator) since I took them off when doing the headers. They wouldn't go back on because the flange of the headers covers the bolt holes on the head. Nothing that a drill can't fix.

 

Well, I got the brace for the alternator back on and ONE of the brackets that goes on the compressor (goes from compressor to the front of the engine).

Anyway, upon further investigation, the NOISE comes from the alternator (or possibly the pwr steering pump - both on driver's side) only when the A/C is on. (A/C compresor is on pass side). No noise from the compressor that I can tell. Do I need a new alternator or to have the A/C pressure checked (thinking maybe it's low making it hard to turn the pulley) ???

I'm beginning to wish I had never pulled the motor apart in the first place.

 

A good way to find noise is with a piece of heater hose. Stick it in your ear (I just love telling people that!!!) and probe around with the other end to locate the source.

 

OK, I stuck it in my ear tonight. Turns out it's the power steering pump making the noise. Its really odd that it only does it when the A/C is on.

Last weekend I reinstalled the brace from the A/C to the front of the engine, and the one from the rear of the alternator to the driver side head. It didn't change anything. I took a breaker bar and applied a little forward pressure on the rear of the alternator and the noise does stop. So it appears to be that something is installed loose. I bought another serp belt in case the vibration was related to slippage - no change.

So, either:
a) The compressor is causing an undue amount of vibration in the system when turned on, or;
b) There is something loose with the way the alternator and power steering pump (and their bracket) is installed on the driver side head.

I am going out of town this weekend, so I will check option "b" the following weekend, unless someone here thinks I am wasting my time and should just have an A/C tech look at it.



Thanks for the ideas so far. I knew about the 'stick it in your ear' trick, but for some reason it didn't cross my mind when trying to find the source of this problem. Keep the feedback coming!

 

Try taking the idler pulley and pushing it downinto the belt and see of the noise goes away. It seems that the long belt travel through where the air pump used to be has something to do with that. Im trying to figure out a wat to put another tensioner or dampener in there to take out some slack.

 

Took the car to a local shop today. They watched while I turned on the A/C. The alternator was vibrating. Looked like bearings? When I took the alternator to Autozone (had a 1 year warranty) they spun it on the table, spun the pulle, etc...and told me the bearing seemed fine. They were reluctant to swap it out but eventually I convinced them. I'll put the new (reman) alternator on it tonight and see if that makes a difference. If not, then it looks like the a/c clutch.

 

OK, swapped out the alternator last night - no change.

It's gotta be the A/C clutch.

Not looking forward to trying to swap that out.

 

Hey check the belt length problem first, I still havent changed mine yet but will soon if you can hold out. Ill let you know.

 

I actually went with a new shorter (by 0.6") belt to make sure it wasn't slippage. Also the routing goes from the crank up to the A/C first, then over to the tensioner, then over to the alternator. The tensioner doesn't really seem to bounce around much, so I think that the A/C clutch is clattering causing it to 'pulse' the belt as it moves over to the alternator.

 

Thats what I was thinking. There is a LONG travel distance between the crank and the A/C. If you watch the belt with the A/C off its fine, but it jumps around when its on. Plus Ive heard that is the belt doesnt cover 45% (I think thats right) of the pulley it might cause it to slip too. I was considering finding an A/C delete pulley and try to retrofit it into where the AIR pump pulley would be. got a sneaky suspicion that would do it. When I put more pressure on the tensioner pulley the chatter goes away completely, making me think its more of belt elasticity as opposed to slippage.

BTW I checked my pressure and found it to be a little low. I put an Oil charge on it and filled the system to the appropriate levels and it quitened down significantly too.

 

I tried to pressure the tensioner a bit and found no real change in the clatter. In fact the only way I was able to get the noise to go away was by putting a long bar from the front of the valve cover to the rear of the alternator and applying some pressure. The 'vibration' was still there, but no clattering. In replacing the alternator I re-tourqued the bolts and all were fine.

I finally found an a/c clutch for ~$65 (dealer only I think). Not sure if I should try that first, or have the a/c pressure checked first. ???

Any thoughts?

 

Definitely pressure, you can get that done free. then clutch

 

I'm in the process of trying to figure out this exact same problem on my bird... When A/C is on and at about 750-800 rpm, the alternator seems to be vibrating... I have a serpentine belt setup, with no air pump... I also have the 120amp b4c caprice alternator.... Off idle, and on the highway, no noise... Just at that one rpm range... Strange... I was starting to think I was the only one trying to solve this mystery.

 

Im working on something else now. Don't think the AC delete pulley will work. I am going to see if a larger tensioner pulley will fit in one of the holes where the air pump was. Im going to do it next weekend and will post results so keep your ears to the ground.

 

OK I finally got around to putting in that pulley I was talking about. And it worked a little. Took almost all the chatter out but she still hums. I took an alternator bolt and the largest idler pulley I could find. Used some brass spacers to fill the gape and washers to make sure it was all stable and bolted it in.depending on how you want to do it will depend on exactly what you need. Good luck.

 

Oh, I fixed my vibration!! It turns out that the outermost bracket mounting bolt (that goes into the head) was about a turn loose. I was just staring under the hood when I saw a very small space between the bracket and the head (we're talking really small). Got in there and tightened it up, and no more vibration.. Strange that it only vibrated with a heavier load on it (a/c on)...

 

Sweet, I need to find a bracket that will work with my headers then. Im sure they make one aftermarket.

 

The bracket I'm talking about is the one that holds the power steering pump and alternator... The bolt connecting it to the head on the drivers side was the one that was a little loose.

 

OK I got ya, Ill have to doublecheck all of them then. Thanks

 

Me too. I'm almost positive that I checked them all, but this news makes me wonder if I missed something. At least it'll be a cheap fix if it works!

 

ok maybe a little off topic but my ac last time i used it when it was engaged smoke came form the belt due to the fact the clutch wasn't moving, is that the clutch or the compressor messing up? the clutch is easier to fix so i'm hoping thats what it is.

 

Did the smoking stop when the a/c was turned off? If so, then its likely the clutch is fine but the compressor is seized.

-- regarding the topic, I found a loose bolt on one of my pulleys. I torqued it back down and the vibration is gone! Thank goodness!

 

so this extra ac bracket (and is there one for the alternator too?), does it help stop vibration only when the AC is running, or all the time???

Also, are those extra brackets only for the V8 or V6 too???

thanks.