Throwing fan belts

[ajducote]

A new problem just started. When my dash air compressor kicks on it also locks up the radiator fan so air will be pulled across the A/C condenser. On my trip this past weekend when the AC kicked on, 1 of the 3 belts that run from the engine to the gear box would get thrown off the pulley on the gear box end. As long as the dash AC is not turned on it seems like the belts stay on.
I hope it is as simple as needing new belts? Or is it something more complicated? Anyone run into this before?

[dale farley]

Andre, If the belts are old or worn, I would replace them and make sure the alignment is correct on the pulleys. Hopefully, that will take care of the problem. I would also check to make sure the compressor isn't locking up, causing the belts to slip on the pulley. Good luck.

[jack14r]

Andre,Also check the pneumatic tensioner and make sure the air pressure is adjusted correctly on the regulator.Prevost has a belt that they call a super belt and it is 3 belts made as one,I don't know if it will fit your coach but it is almost impossible to throw.

[flyu2there]

That sure sounds like one of the belts is stretched...change all of them!

John

[adamdegraff]

It sounds to me like your AC compressor might be locking up. That happened to me and it screwed with all the belts west of the alternator. (Assuming your air tensioners are all good.) This was the diagnosis of the guys over the phone at Prevost. I put in a new drivers AC, new AC clutch, and poof, the problem was fixed. Depending on where you are located I can give you the name of a place to get it done right and for not too much money. Let me know.

~Adam

[ajducote]

Thanks everyone for the suggestions. I do not believe it is the AC compressor, it was replaced a year ago and it makes REAL cold air, so I think it is working fine. I suspect the belts need replacing, I will try that 1st and I like the idea of checking the air pressure for the tensioner bags. I had not thought of that. I will change the belts tomorrow and report back on results.

[adamdegraff]

One other thought...
the roller on the fan belt, I am told, has a bearing in it that tends to go bad. It is small, which means it turns way more times than the big pulleys. And it would also make sense that with the AC on, this might be getting more play since the fan runs more often when you are calling for AC. Also, even if your AC compressor is working perfectly, the clutch could be bad. Did you change the clutch at the same time you changed your compressor? If I remember correctly, the clutch was about 3X the price of the compressor!

Good luck. Hope it is just a bad belt.

Adam

[truk4u]

Andre,

If I remember correctly, the regulator pressure is suppose to be 40 - 50 lbs. I assume you know it's above the engine access doors and is checked with a standard tire gauge.

[ajducote]

I checked the air pressure and it was only set at 35 psi. I adjusted it up to about 48 psi and tested and it seems like the belts want to stay on now. So it may have been as simple as low pressure in the bags. I guess on my next trip I will find out.

[Pete]

Andre, while you have the belts off, push the platform that holds the A/C compressor and transfer case (CAREFULLY) toward the radiator to make sure it cannot touch the radiator. I can speak from personal experience that a belt set-up that is too long can crash the fan clutch assembly into the radiator.....a very expensive situation!. A new radiator from prevost is only $3,000.00.

I was lucky and was able to have mine repaired, and with a another fan clutch assembly, the repair was only $2,200.00.

I also put a new set of belts that were shorter than the originals, and modified the platform assembly so it would not be able to touch the radiator should the belts come off.

The fins from the clutch assembly broke off and went through the radiator in about 4 or 5 different places.

If I ever figure out how to post pics, I will do so.