89 Suburban V2500 Belt Slips back on AC

[daneff74]

We have a 1989 GMC Suburban V2500 with the 5.7 engine, A/C, power steering and no smog pump. While the AC was not working we had no issues with the belt. Once we repaired the AC system the belt was shreaded with in a few miles. Once we replaced the belt we noticed that there was no movement until the A/C compressor engaged then the belt jumped back towards the compressor instantly.

Installed a new belt (96 1/4) slips at start up and compressor not engaged
Tried a shorter belt (95 1/4) slips back when compressor engages and came into contact with the upper compressor bolt.
Tried a medium belt (95 3/4) slips back when compressor engages and came into contact with the upper compressor bolt.

We drove this vehicle 700+ miles with no A/C. Once home we replaced the idler pulley and tensioner pulley, just bacuse it sat for 10 years at a hunting cabin. Later we noticed the belt had moved back towards the engine. Since the alternator was over charging we replaced it and noticed the old pully was a 5 grove and not a 6 like the new one. The belt fit the new alternator better, it did not look like it was riding high on the front and back of the pully. Now that the alternator was replace we worked on the A/C and several attempts and two slow leaks later, we found a leak on the back of the compressor, because of this we figured it was oil from the compressor causing the belt to slip. During the filling of the A/C system we noticed that the belt had slipped again. So we shut it off, repositioned the belt and double checked that everything was aligned and it still slipped backwards. So now we tried different belt lenghts.

Installed a new belt (96 1/4) slips at start up and compressor not engaged
Tried a shorter belt (95 1/4) slips back when compressor engages and came into contact with the upper compressor bolt.
Tried a medium belt (95 3/4) slips back when compressor engages and came into contact with the upper compressor bolt.

Now we are lost in tring to figure this out. Right now dad is going to finish charging the A/C system, then hope we find answers to why this is happening.

I do have a concern about the brackets used to mount the A/C alternator and power steering pump. I purchased the full GMC service manual for the 1989 years and noticed that the backets shown in book match the G series van and not the V series suburban. I did check Rockauto, Autozone, and Advanced auto and confirmed the part numbers for the Idler and tensioner are all the same.

This is what we have, A/C on the right side:

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This is from the book for a 5.7 (350) which shows the A/C on the left side

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This is from the book for the G-Series with a 5.7 and the image at the top left matching the aluminum brackets and positioning we are seeing.

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[daneff74]

I wanted to add in picutes of the belt install label on the fan shroud and a pic from the left side of the engine. Also note the the long belt has now shreded off one groove as we continued to charge the A/C system.

 

[GoToGuy]

The G series is the Van. You have the cast aluminum mount bracket. I believe your should have the steel plate. The aluminum came out later. Have taken a straight edge to check all pulley are in the same plain. With no load a .out of whack pulley will track but when load is applied it will drive the belt off. Possibly.
Are you using the truck manual? The van , G body is unique to vans . The truck platform, Tahoe , sub, etc gas all have compressor on right side till 96 and Vortec introduced.
On the tensioner is diamond and a scale where new belt tension is correct. This is in the same section

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