A/C Compressor Vibrates

[bcomo]

I had the engine running with the A/C compressor on while I was under the hood. I've never had it on while I was working under the hood before this.

As I race the engine, the compressor vibrates forward and backward, enough to see it very visibly.

I checked the bolts on the brackets to the engine, and the bolts on the compressor to the bracket. They are tight.

When my engine was rebuilt, they had to recharge the A/C. Could this be happening because it's overcharged and laboring the compressor???

Also, the A/C belt is very tight, more than I would like to see -- could the belt be too tight and the compressor is vibrating because of that???

Any ideas -- or can someone with an A/C unit run their A/C and race the engine from under the hood to see if this compressor vibration is common?? Asking alot, I know.

[Guest]

Dont know much about AC but heard if you change from the old type of freeon(R12?) to the (R132?) that you use 20% less.
Check into that for the correct info.

[bcomo]

Thanks EG.

My system was recharged with the old R-12 stuff; if that means anything -- I don't know.

[ncbird]

Bart is the actual compressor body moving? how can it do that if it is bolted tight? Could it be that it looks like that when the clutch engages? The clutch does come forward when it engages and slides back when it disengages.
Grant

[bcomo]

Grant:

I started it up and took another good look at what's happening.

This only happens with the A/C compressor on.

It seems that at between 1500 and 2000 RPM, the A/C belt between the fan pulley and A/C pulley oscillates (vibrates) at about 1/2 inch up and down between the two pulleys. Between that RPM it vibrates so much that the compressor actually vibrates because of the vibration caused by the belt.

Above 2000 RPM or so, the belt smooths out without vibration, and the compressor doesn't vibrate either.

Yes, the A/C belt is tight -- actually tighter than it should be (about 1/4 inch flex).

If the A/C is not on, this does not happen -- everything smooth at all RPM's.

So why is the fan belt vibrating with the A/C clutch engaged? Is it the drag on the clutch only between 1500 and 2000 RPM that is causing a harmonic vibration and the belt vibration???

Never saw this before in my lifetime.

[ncbird]

Bart thats very strange. My immediate reaction would be clutch.. maybe the air gap is off and it isnt fully engaged. I guess I would go back to the last thing done to the A/C and have a second shop check the charge level to make sure it isnt to high which I understand can make the compressor noisy...and have them check the clutch. I am assuming that the fast idle is working when the A/C comes on. Do you hear any clicks when this is happening?

[tbird430]

From a side veiw, are all the pulleys belts lined up "square" to each other?

[bcomo]

The pulleys and belt lines up perfectly.

I took it to a different shop and asked a guy that I trust to check the charge level, He showed me the gauges, and said that it was right where it was supposed to be.

His thoughts are similar to yours Grant; that the clutch may be doing something not right. But what????

I can see that the belt is riding high in the groove. I wonder if that could be something. Does anyone have a Gates # for an A/C belt on the 430? The Ford PN doesn't give me any specs.

[Guest]

Bart I have the same problem with the AC in my big truck.(Freightliner) the problem is someone before me changed the pulley on the altenator (smaller pulley) causing there to be not enough belt contacting the AC compressor pulley

[bcomo]

George:

Thanks for the input --

On mine, I can see that the wear is on the upper part of the "V" of the belt. It looks to me that the belt needs to be a narrower "V" angle so that it can ride lower in the groove.

What did you decide to do about this situation on your truck? Will it hurt things to keep running it like that???

I'm still hoping that someone can give me a "Gates", or non-Ford part number on their A/C belt. This way I can look up the width, and V angle specs from a cross-reference on the Gates web site.

Maybe I have the wrong belt.

[GTE427]

Bart,

I found some info on the 430cid Air Conditioning belt specification. In the AMA Specification, 60 Thunderbird, Issued 9-15-59, the specs for a 60 430 air conditioning drive belt is:

Angle of V: 36 degrees
Nominal Length (SAE): 44.24
Width: .50

[bcomo]

Ken:

Thanks very much for finding that.

The gates belt that I have now is the same Angle of V, and width. It's 1/2 inch shorter, but that wouldn't matter.

It looks like the belt vibration is from another issue, still to be found.

[Alan H. Tast, AIA]

AMA Specification

I've been trying to find a copy of the AMA specifications - I had one over 20 years ago for a '60 and a '61, but various moves over the years have misplaced it. Where did you find it, and/or is it possible to arrange for a photocopy of it?

[GTE427]

Alan,

I found this at one of the many literature dealers at Carlisle in the past. It's a reproduction , 28 pages and I would gladly send you a copy. PM your mailing address and email, if I can scan it I'll send a pdf, otherwise USPS.

[bcomo]

I'm very frustrated

OK -- I am really frustrated on this AC belt vibration.

I put a new AC belt on this AM, using a leverage bar -- so the flex in the belt is less than 1/2 inch.

When the car runs at idle without the AC engaged, the belt still flops up and down alot between the fan and AC pulleys.

Then, when I put the AC on, the belt vibrates up and down so much that it almost looks like it wants to jump the pulley -- it's that bad untill the RPM's climb over 1500

Can someone give me a comparison by running their engine at idle and see if the AC belt vibrates that much with the AC ON?

Thanks in advance.