ac belt loose vibration problem
Thread Starter
Instructor
Joined: Jul 2006
Posts: 237
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From: walker louisiana
ac belt loose vibration problem
anyone had the problem of ac belt vibrating at idel???..its loose on the bottom side cant get it tight enough to stop....its on a stock 77 l48...im going to a surp.system later but for now this sucks.. thanks
Last edited by rweasterly; Jun 22, 2007 at 05:52 PM. Reason: left out something
Thread Starter
Instructor
Joined: Jul 2006
Posts: 237
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From: walker louisiana
my bal. is fine...and i got a shorter belt so i would have more ajustment....its strange when it is idleing the bottom side of the ac belt is moving like crazy....this is not my first c3 but it is the only one to do this.....thanks for the reply
Burning Brakes
Joined: Dec 2005
Posts: 992
Likes: 56
From: Baldwinsville, NY
78 L48 with AC
Have the same problem, took the alternator and AC belts to NAPA and both were like new. The Alternater seems to short and there is only 1/2" of adjustmert from "O" but the AC is almost too long and I use all but 1/2" and the belt jumps on the bottom and hits a belt shield when at idle. Let me know if the shorter belt stops the jumping when at idle.
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Ah ha! You have a 77 - I've never met a parts store that had this right in their computer. You're probably getting the wrong belt - early 77s still had the A6 compressor, later models got the R4.
Thread Starter
Instructor
Joined: Jul 2006
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From: walker louisiana
mine has been changed over to the newer refg....but what does the compressor have to do with it...and what is the fix??the compressor looks just like the one that came on it..
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
The A6 and R4 compressors are physically different. They require different length belts. Is the compressor long and bulky, or does it look like a short, fat pancake? Trust me...you can't get an A6 belt to work right with an R4.
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Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
I know almost all the 68-73 sb cars with the A6 compressor does this same thing. In like 75' I think, chev made a guard that bolts in over the lower radiator hose to keep it from getting rubbed on by the belt. So instead of fixing the belt wobble, they made a guard....LOL
Its normal, not sure why, but they all do it. Been like that for 38yrs so I wouldn't worry about it. Mine hits the hose from time to time so I cut another section of hose and wrapped in around in the rub area just for extra "protection"
Its normal, not sure why, but they all do it. Been like that for 38yrs so I wouldn't worry about it. Mine hits the hose from time to time so I cut another section of hose and wrapped in around in the rub area just for extra "protection"
Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
Belt vibrates or jumps because of 2 things. Span between the pulleys.and because the compressor pulses as it compresses the refrigerant. everytime the piston compresses the fluid the pulley speed slows a bit then it unloads and the next piston starts its compression stroke. Set tension so you have approx 1/2 deflection of belt when pressure is applied.
A jumpy belt is of no concern unless its being thrown off the pulleys.
The only way to rid yourself of the condition is to put a tensioner on the belt.
A jumpy belt is of no concern unless its being thrown off the pulleys.
The only way to rid yourself of the condition is to put a tensioner on the belt.
Melting Slicks
Joined: Jan 2004
Posts: 2,527
Likes: 1
From: St. Petersburg, Fl///Columbus, Ohio
Belt vibrates or jumps because of 2 things. Span between the pulleys.and because the compressor pulses as it compresses the refrigerant. everytime the piston compresses the fluid the pulley speed slows a bit then it unloads and the next piston starts its compression stroke. Set tension so you have approx 1/2 deflection of belt when pressure is applied.
A jumpy belt is of no concern unless its being thrown off the pulleys.
The only way to rid yourself of the condition is to put a tensioner on the belt.
A jumpy belt is of no concern unless its being thrown off the pulleys.
The only way to rid yourself of the condition is to put a tensioner on the belt.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 237
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From: walker louisiana
i have thought about the tensioner idea and i have one...i will have to see if it can be made to work...and i have to disagree with living with it/nothings wrong/its not going to hurt anything...im looking for a fix not a vibration i will have to live with...i have had a 77 78 79 82 all with the same ac system ... this 77 i have now is the only one that has done this....if i find a way on my on to fix it i will sure post it, because i cant be the only one tha does not want to just live with it....and !!!!!!!!!! yes i do want ac....thanks and i will keep you posted
Thread Starter
Instructor
Joined: Jul 2006
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From: walker louisiana
simple fix
simple fix...i took the idlr pully off a gm surpentine system i was going to use...loosen the ac to get slack in the belt...installed the pully below the ac comp using the bolt hole that is there for the small round bracket that runs to the bottom front of the block(around the crank area)then tightn the belt and that was it... i havent put any miles on it yet but i will let ya know...i will probably tinker with it somemore but for now it works without any holes to drill nor brackets to make.....pulley is off a gm/chevy truck surp. system...the pulleys are pretty much the same...
