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Belt squealing on 1999 Dodge 3500 Roadtrek Van

The belt squeals on my van, mainly when I am accelerating with the AC on. If I turn the AC off and then accelerate I don’t get squealing, and once up to speed I can turn the AC back on.
I’ve replaced the belt multiple times, and also the belt tensioner several times, to no avail. I’m thinking about raising the AC head using some spacer washers to try to get some additional tension on the belt.
Any ideas?

Given what you’ve done already, I doubt the problem is that there isn’t enough belt tension. When the AC is on there’s more tension along the entire belt path, so I’m guessing the squeal is coming from some other problem along that path. Like the AC compressor itself. If this happens in the driveway when you bump the rpms by diddling the throttle, have a helper use a piece of garden hose as a stethoscope to try to narrow down exactly what part is doing the squealing. Placing the tip of a big, long screwdriver against the AC compressor and listening to the handle end of the screwdriver can locate compressor noises too sometimes.

Another idea, get a spray bottle with some water in it and spray it on the belt when this is occurring. If the noise stops, almost has to be either the belt or one of the pulley’s.

Yet another idea, the belt tension is usually spec’d. Like it will say 1/2 inch deflection at a certain midway point with 4 pounds of force applied. I had to set the belt tension in an appliance a while ago, and used my 4 pound BIG hammer (as a weight) to get the deflection what it was supposed to be. I could have easily adjusted it much tighter, so the hammer method turned out to be a good idea. The hammer has “4 lbs” stamped right on it, how convenient!

Thanks for the suggestions, George. I tried listening for noise from the compressor and also the alternator using the hose method and listening through a long stick. Neither one identified the squealing as coming from a bearing. I took the belt off and sanded the pulley grooves thinking they might have been glazed. No help at all. Eventually what did solve the problem, at least for now, was taking off the Gatorback belt and putting on a used Dayco belt. Stretched next to each other the Gatorback seemed to be just slightly longer. I had replaced the Dayco belt a few years ago, because, you guessed it, it was squealing. So this may be a temporary fix. Will find out in the next few days, as I have a long trip to a hot climate.

Folks here seem to like Gate’s branded belts, if that is of any help. Good job on verifying the problem is from the belt or something on that belt path. That narrows it down. Did you try hand rotating the various pulley’s when the belt was off? Notice any unusual noises or binding? I’m guessing you are very close to a solution.

Made it through 3000 miles this summer with very little squealing. Won’t be driving it much until next year, and I think I’ll put on a Gates belt as you suggested. Thanks for your help.

That’s 3000 miles of good news. Great! Thanks for keeping us updated on your Van’s progress.