accessory belt comes off

**94VERTiGO** · 07-02-2007, 07:35 PM

'94 suburban, 5.7L, 2WD.
Belt came off Thursday last week while wife driving. I went and put the belt back on, it was pretty tore up so I went straight to auto parts store and put on a new one before driving home.
Next day, new belt came off again while she was driving. I went and traded cars with her and drove the sub back to work and later home that evening.

Belt never came off with me driving, but I didn't run the A/C. So I started it in the garage put on the A/C and when I revved the engine (by hand at the TB) I could see the belt skirt across the idler pulley (located directly beneath the A/C compressor).

Got my wife to sit in the truck and turn the steering wheel with the A/C running and the belt skirted across the pulley.

Any ideas?
Has the tensioner pulley just started to wear out and the load on the belt from the A/C and turning making it fail?
By the way, I replaced the idler pulley (directly under the A/C) but it didn't make a differnce.
Thanks,
Pat

**GaryL** · 07-03-2007, 10:34 AM

Is your AC compressor making any new noises? If it is starting to try to bind up, I can see the tensioner moving a little more with the added load and causing slack in the belt as it bounces back into place and letting the belt move out of place. Just a thought.

**94VERTiGO** · 07-03-2007, 09:09 PM

Thanks, but no noise from the A/C compressor, it and turning the wheel just cause too much load on the belt.

The tensioner pulley seems to move all the way in the way in the down position so it is oriented completely verticle. It still has plenty of tension on it, as it takes a breaker bar to release it. I wonder is the belt a little too big?

There were about 6 belts to choose from with this truck, and we put the same part number that came off of it. Although we never had a problem with the belt in 180,000 miles, something is going on.

Maybe I will try to find a smaller belt.

**Cableguy** · 07-03-2007, 09:19 PM

Did you keep the original belt or did you throw it out yet? I would compare size at store. Either that or a bearing is going in another accessory? Hard to tell without being there to see what is making it walk off.

**Rumpamuro** · 07-04-2007, 02:44 AM

try getting the wife back in there, start the engine, watch the movement of the tensioner, then tell her to turn the a/c on, examine the tensioner, then turn the wheel and examine the tensioner, see if there is ample amount of movement from no a/c to a/c and turning the wheel and most likely u found your problem.

**84fiero123** · 07-04-2007, 08:32 AM

Take the belt off the tensioner and wiggle the tensioner pulley, it should not wobble, if it does the tensioner bearings are shot. Replace the tensioner if that is the problem.

**94VERTiGO** · 07-09-2007, 06:30 PM

Tensioner applies plenty of pressure to belt, the pulleys on tensioner are good and tight, no wobble at all.

I have since given up all hope and took it to the mechanic. I will keep you all posted.
Thanks for the suggestions and comments.

**94VERTiGO** · 07-13-2007, 11:20 PM

It was the belt that was the wrong size. Funny, but I had run this belt for years and now it decides to come off.
I believe the alternator voltage was the deciding factor on the belt size.
The correct belt was a 955, I had a 970 on it.
The key to knowing you have the correct size belt is the arrow on the tensioner, it should line up at the mark 2 straight lines(||)at the middle of the solid (non-rotating) part of the tensioner. See picture.

**unplugged** · 07-17-2007, 04:44 PM

Sorry I didn't catch your post in time. This was the exact problem with my 93 burb. I bought a new belt and got the one that was for the model with air pump and mine didn't have one. The belt fit, but it was loose. I did save the original and it was closer in size to the non-airpump belt. The intermittent problem of the belt jumping off has ended. Sadly, I had replaced the idler and tensioner pulleys first, thinking that was the problem.

**Cableguy** · 07-17-2007, 07:46 PM

Originally Posted by 94VERTiGO

It was the belt that was the wrong size. Funny, but I had run this belt for years and now it decides to come off.
I believe the alternator voltage was the deciding factor on the belt size.
The correct belt was a 955, I had a 970 on it.
The key to knowing you have the correct size belt is the arrow on the tensioner, it should line up at the mark 2 straight lines(||)at the middle of the solid (non-rotating) part of the tensioner. See picture.

Oh for the love of gawd. I have done that by accident too. Its like walking into a screen door when you thought it was open. Then you look around to see if someone seen you do that.