A/C belt vibration
Thread Starter
Racer
Joined: Aug 2000
Posts: 364
Likes: 3
From: Van Wert Ohio
A/C belt vibration
My '79 A/C belt starts vibrating at about 3000 RPM (about 65 MPH). It's only when the compressor kicks in and it's a harmonic - not all the time. Drop to 55 MPH and it goes away. Any tricks?? Belt tension or type?
It's a rebuilt R4 compressor set up with R134. I had the vibration with R12 as well.
It's a rebuilt R4 compressor set up with R134. I had the vibration with R12 as well.
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by Bobchad
Most report vibration at idle that goes away when the rpm's go aboe 1,000.
Mine does at 600 rpm. First thing I would do is try changing the tension. Second thing would be to switch to a Dayco Topcog. They seem to ride lower in the pulleys.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Over the years I suspect the old tooling for V belts has been changed over to metric, and so the width across the back is differant than it was, AND the taper to the V section is differant also.... what seems to happen is the backside of the belt allways looks pinched in and ( shaped in profile instead of flat, after running for a while on these old cars.....looking at the belt V surface seems to prove the point as the wear is at the top of the V and not the bottom so much....
I think there must be a source of the old 'American' style V belts that would function much better for these cars, but don't know of any....throug the years I have had many troubles not only with that R4 vibration, but belts squeeling, and other symptoms....
GENE
I think there must be a source of the old 'American' style V belts that would function much better for these cars, but don't know of any....throug the years I have had many troubles not only with that R4 vibration, but belts squeeling, and other symptoms....
GENE
Instructor
Joined: Dec 2002
Posts: 242
Likes: 0
From: Port Orchard Washington
I would agree that your harmonic is caused by the belt not riding in the groove properly. Try to find a different manufacturer that you can compare top widths of the belt and get the narrowest to fit deeper into the pulley groove. I have seen many older chevy's that had rust and crud built up in the bottom of the pulley groove and a polished upper grove indicating that most belt manufacturers have increased the cross-section of the belts.
