I have a vibration caused by the AC compressor
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Joined: Nov 2013
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From: Nashville Tennessee
I have a vibration caused by the AC compressor
I have a 1986 C4, when I have the AC on, I feel a vibration in the engine that changes with the engine RPM. The air was working fine, but I changed the compressor anyway, thinking that would fix the vibration, but it didn't. I replaced the belt tensioner, that didn't change anything either. I've checked for loose brackets, and anything that might be rubbing the compressor, but I haven't been able to find anything that appears to be wrong. Any ideas would be greatly appreciated.
Melting Slicks
Joined: May 2014
Posts: 2,897
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From: New Port Richey FL
Did you make sure your high and low side pressures are in the proper ranges. you might have a clogged orifice or some other part. If pressures are not rite it can cause a high effort on the A/C pump pistons. Take a second look. Also when you replaced the Compressor did you just bleed off the gas throw in the compressor and just refill with one of those do it yourself fill kit, don't get me wrong refilling yourself kits are OK when used properly but when you open the System it needs to be drawn down and evacuated.
The proper amount of gas and A/C oil also needs to be used
After though was the a/c system properly converted from R-12 to R-134? I doubt most people have any R-12 still around the house stuffs kind of Rare to find now.
http://www.ecklerscorvette.com/corve...1985-1987.html
The proper amount of gas and A/C oil also needs to be used
After though was the a/c system properly converted from R-12 to R-134? I doubt most people have any R-12 still around the house stuffs kind of Rare to find now.
http://www.ecklerscorvette.com/corve...1985-1987.html
Last edited by s carter; Sep 10, 2015 at 10:15 AM.
Thread Starter
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Joined: Nov 2013
Posts: 51
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From: Nashville Tennessee
Did you make sure your high and low side pressures are in the proper ranges. you might have a clogged orifice or some other part. If pressures are not rite it can cause a high effort on the A/C pump pistons. Take a second look. Also when you replaced the Compressor did you just bleed off the gas throw in the compressor and just refill with one of those do it yourself fill kit, don't get me wrong refilling yourself kits are OK when used properly but when you open the System it needs to be drawn down and evacuated.
The proper amount of gas and A/C oil also needs to be used
After though was the a/c system properly converted from R-12 to R-134? I doubt most people have any R-12 still around the house stuffs kind of Rare to find now.
http://www.ecklerscorvette.com/corve...1985-1987.html
The proper amount of gas and A/C oil also needs to be used
After though was the a/c system properly converted from R-12 to R-134? I doubt most people have any R-12 still around the house stuffs kind of Rare to find now.
http://www.ecklerscorvette.com/corve...1985-1987.html
Last edited by lugnut67; Sep 10, 2015 at 11:31 AM. Reason: forgot to mention something
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Joined: Nov 2013
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From: Nashville Tennessee
The pressures are correct, I did wonder if there could be too much Freon in the system, so I was running the engine as I drained off the old, The vibration never went away. As for the new compressor, I haven't fully charged it, (only 2 cans), so I'm sure that it isn't over charged. I just have the feeling that the vibration is caused by something external, ???
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From: Nashville Tennessee
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From: Ocean Springs MS
I recall a factory service bulletin on R4 compressor noises. It called for some added bracing for other cars and trucks to eliminate the vibration. Don't know if they came up with a modification for Corvettes. I have an 85 and it makes an awful vibration at certain low RPM. I have replaced the compressor several times, and they all do it. I wish there was a good fix for this.
Cruising
Joined: Jun 2015
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A/C compressor vibration
I had a similar problem. Replaced the A/C compressor bearing and the noise was the same. Turned out to be a small crack in the compressor aluminium mounting bracket. A previous mechanic had removed and replaced the compressor but did not replace the long bolt that goes through the bracket and into the block. Hard to reach behind the compressor pulley.
Over time, forces on the bracket cracked it. That bolt must always be reinstalled.
The test is to very carefully press down on the belt tensioner arm with a long piece of wood, and observe the compressor bracket for a crack, or a change in the noise.
Over time, forces on the bracket cracked it. That bolt must always be reinstalled.
The test is to very carefully press down on the belt tensioner arm with a long piece of wood, and observe the compressor bracket for a crack, or a change in the noise.
Thread Starter
Advanced
Joined: Nov 2013
Posts: 51
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From: Nashville Tennessee
I recall a factory service bulletin on R4 compressor noises. It called for some added bracing for other cars and trucks to eliminate the vibration. Don't know if they came up with a modification for Corvettes. I have an 85 and it makes an awful vibration at certain low RPM. I have replaced the compressor several times, and they all do it. I wish there was a good fix for this.
Thread Starter
Advanced
Joined: Nov 2013
Posts: 51
Likes: 2
From: Nashville Tennessee
I had a similar problem. Replaced the A/C compressor bearing and the noise was the same. Turned out to be a small crack in the compressor aluminium mounting bracket. A previous mechanic had removed and replaced the compressor but did not replace the long bolt that goes through the bracket and into the block. Hard to reach behind the compressor pulley.
Over time, forces on the bracket cracked it. That bolt must always be reinstalled.
The test is to very carefully press down on the belt tensioner arm with a long piece of wood, and observe the compressor bracket for a crack, or a change in the noise.
Over time, forces on the bracket cracked it. That bolt must always be reinstalled.
The test is to very carefully press down on the belt tensioner arm with a long piece of wood, and observe the compressor bracket for a crack, or a change in the noise.
Instructor
Joined: Apr 2003
Posts: 204
Likes: 9
From: Ocean Springs MS
My vibration is just off idle, about 900 RPM, doesn't do it any other time. I have looked for ways to come up with another brace for the compressor, but never could figure out a way to attach anything. It may be possible to retrofit a totally different type of compressor in there, but I would not really want to do that.
Burning Brakes
Joined: Apr 2011
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From: College Station Tx
Not sure about your model, but on the 95 there are 2 braces that go from the compressor to the exhaust manifold. The PO of my car installed shorty headers and didn't reinstall the braces. I purchased a set of used braces here and the vibration went away after installation.
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From: Nashville Tennessee
My vibration is just off idle, about 900 RPM, doesn't do it any other time. I have looked for ways to come up with another brace for the compressor, but never could figure out a way to attach anything. It may be possible to retrofit a totally different type of compressor in there, but I would not really want to do that.
Thread Starter
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Joined: Nov 2013
Posts: 51
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From: Nashville Tennessee
Not sure about your model, but on the 95 there are 2 braces that go from the compressor to the exhaust manifold. The PO of my car installed shorty headers and didn't reinstall the braces. I purchased a set of used braces here and the vibration went away after installation.
Melting Slicks
Joined: Jun 2013
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I also have a slight vibration that I can feel too when my A/C is on on my 1985. It's barely noticeable, and only happens from idle to 1500 RPMs. I figured it was my cam causing the vibration because the engine bumps around a lot more with a cam. I'm not worried about it. But maybe next time my compressor is off, I'll check for cracks.
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From: Nashville Tennessee
It doesn't sound like your cam is going to be the problem. I took mine off just to check, there wasn't any problem with the bracket. I cleaned the mounting surfaces and tightened all of the bolts evenly, then I put rubber between the smog pipes and anything that they come close to. The vibration seems a little better, but hasn't gone away. Now I have a stalling problem. It is showing a #42 code which is suppose to be for the automatic timing control. Could be the ECM, I've changed the ignition module. I can't seem to catch up with this thing ????