[Archived]

it was done a number of years back . Do not remember what was required. Will look up the invoice.Sorry

[Bill]

The alternator is bolted to the engine bracket by four bolts, through/from the bottom.

Be sure the bolts are in place tight and not broken or stripped.

JIM

[Archived]

If the pulley is like the one I have had on my coaches it is on a splined shaft and while the alignment of the 50DN is important, it is equally important to make sure the pulley has a little bit of come and go. That compensates for slight imperfections in alignment. Could it be rusted in place so it does not slide in and out?

The mechanical jack screw adjustment on the belt also has to be right and the tension should be checked with a device that verifies the proper tension. Lastly, If I remember correctly there is only one pully driving the serpentine belt, and with the exception of the 50DN driven pulley, all others are idlers. I have found several over the years in need of replacement or new bearings. I would verify they all rotate noislessly with no wobble or growling.

[Gerald]

I
don’t get it. If the belt has the correct tension and alignment, how
can a load on the alternator throw the belt? I had several coaches
with the manual adjust and kept the tension in check with the belt
gauge and never had an issue, even after dry camping with a high load
on start up.

Gerald,
since you’ve lost two belts, have you checked the alignment? I may be
able to get my hands on the belt gauge if you want to keep the manual
setup.

[Craig]

Thanks for all the ideas. There may be a slight alignment issue. Jon, I wasn’t aware that the idler pulleys are supposed to move on their shafts. I’ll check.

The belt stays on as long as I check and retension to 200+ lbs regularly. I use the “cricket” tension gauge. It is not perfect but gets you in the ball park. Before this trip I noticed that the belt was not quite as tight as it should be. But I did not have the breaker bar with me to tighten it. Sure enough I lost it.

This must have been a common problem in the late 90’s since Detroit/Prevost went to the automatic tensioner right after my model year. In my setup, the alternator belt only wraps around 180 degrees on the alternator pulley, with the new tensioner it is more like 210 degrees. The automatic setup is an all around better solution for the poly V belt but from what I read it is not maintenance free either. They seem to last about 100k and then start jumping and should be replaced.

[Larry & Diane]

Without checking I can’t tell you how much in and out play there is on the alternator pulley, but I do know there is a small amount. What is more important is if the angle of the pulley with respect to the belt is 90 degrees. On that there should be no error.