Help with factory A/C belt tensioning

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tkelley72

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Feb 1, 2013
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My Car
72 mustang convertible
Does anyone have a trick for getting the belt tension right on a factory A/C compressor set up? I am having an issue with belt slap and squealing. I have plenty of adjustment left with the idler pulley but just cant seem to get it tight enough to keep it from squealing and slapping around. The belt looks OK but maybe its gotten hard? It's one of the "notched" style belts, not the typical old style V belts. Very aggravating. Any suggestions would be appreciated. Thanks
 
There is typically a 1/2" square hole in the front of the adjustment bracket for tensioning purposes. I use a 1/2" short ratchet extension on my ratchet to hold the belt tensioned while tightening the bracket hold down bolt. Mine has a 351C engine.
 
I tried that, but still can't pull it tight enough to reduce enough slack that the squeal and belt slap stops. I bought a 24 inch long breakover I plan to try to see if I can get more leverage. Thought maybe someone might have tried something I hadn't thought of. Thanks for your input.
 
There is a product called "belt dressing" that I used years ago. It is an aerosol spray you apply to the tapered belt surfaces that gives the belt better grip on the pullies and reduces/eliminates squeaks. Got it at a local car parts store. Idler pully and or/ AC clutch bearings can also squeak when they are going bad.
 
There is a product called "belt dressing" that I used years ago. It is an aerosol spray you apply to the tapered belt surfaces that gives the belt better grip on the pullies and reduces/eliminates squeaks. Got it at a local car parts store. Idler pully and or/ AC clutch bearings can also squeak when they are going bad.
You can also use a bar of soap as belt dressing.
 
Ford had this issue and some cars were equipped with a second fixed idler. Supposedly the heavy steel flywheel clutch on the compressor was a fix for belt slap and noise.


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I don;t have any new trick for you to try with the arrangement you are dealing with. But, I do have a suggestion for other belt driven items (alternator, power steering, aftermarket air conditioning compressors, etc.) that may be of help. For many years, when I had to toghten the belt for alternators and power steering pumps, I would use a pro bar placed carefully so I would not crack or dent the housing of a driven unit, and pull like hell while tightening the adjustment nut.

Well, the other year I was wrapping up a water pump replacement project on our 1973 Mustang Convertible with a 302 2v engine. As easy it it seems that kind of job on a 302 ought to be, it has plenty of of its little challenges, Anyway, after getting the new water pump installed, andall the power driven accessories were back in position, it was time to install the drive belts. About the time I was preparing to tighten the power steering pump I realized the aftermarket azir conditioning compressor was located precisely in an area I would normally be able to use as a leverage point with my trusty pry bar.

As luck would have it Lynda was video recording the project's progress as I narrated. When I mentioned I had to come up with a different way to tighten the power steering pump because of the A/C compressor's location she spoke up. "Here, hold my iPhone (camera). I have an idead." She came back with a nylon rope. Before I had a chance to ask her what she had in mind she said," I bet this works great." She simply strung a length of the nylon rope behind the power steering pumps exterior and when she had a loop in the rope in one hand, while the rope was looped over the pump exterior, she gave the rope a tug. "See if that is tight enough," she said. It was. So, I had her let the rope loose, and tried out her simple but brilliant way to tightening accessory devices without being concerned about denting or cracking anything. I used her technique on the power steering pump successfully, and later I used it with the alternator with the same kind of good result.

I covered Lynda's idea on the video in the link below, at 07:08 mm:ss or so into the recording session.

https://youtu.be/GMZKphUiyj0

If there is no other good idea I ever share with my fellow enthusiasts, this one alone I am most excited about as it touches so many other folks having to deal with tightening drive belts. Kudos to Lynda! She is really one hecl of a wonderful Mustang/Shelby Chick.
 
My trick is to put a hydraulic lift with a piece of 2x4, or whatever works under what you need tightened. I only have one arm that works and I have to figure out things like this all the time. I have a solid piece of an aluminum bar that I use on some things too.
 
I bought one of these belt tighteners
 

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