fan belts breaking

[christopher]

i just replaced my fanbelts that run the alt on my 6v92t. i had three of them on and they broke.
the alt was rebuilt about a 2 years ago. what would cause this?
thanx
chris
mci5c

[grantgoold]

Have you checked alignment of the pulley? How about vibration at RPM?

Are you buying the belts from the same vendor of the same batch?

Grant

[rdbishop]

Chris,

You didn't say if the alt. froze are not. Did the belts burn thru or just break? My alt. is a 225 amp belt driven and I've had it rebuilt 3 times at three different shops, and nobody could fix it right. I decided to open it up myself to see if I could determine what the problem is. Looks like it heats up, expands and everything is dragging on everything. Anyhow, I'm going to try one more shop after labor day. Maybe this time......

Richard

[Sammy]

With the engine not running and the engine start circuit disabled, remove the alt drive belts. Does the Alt spin free?.
If it spins free - disconnect the field wire on the back of the alternator, cover it with a piece of rubber hose and some electrical tape, start the bus and see if they break again. Your alternator might be full fielding, breaking the belts. Let us know what happens.
Sammy

PS. RD, check out Kirk's for a real good rebuilt unit...........http://www.kirksauto.com/index.htm

[Sojourner]

Whenever you downshift either by hand shift or depress pedal quickly...will cause heavy alternator spinning from a given RPM to a sudden faster engine RPM...result belt to jump or snap.
Be sure you have the OEM spec belts. It is tougher belt to handle sudden RPM change of two spinning components.
And check alignment.

FWIW

Sojourn for Christ, Jerry

[jjrbus]

Are you buying a matched set of belts? Belts are made in a long tube and then cut into belts, you want three that were cut off next to each other. Belts are numbered so you want three with consecutive numbers. Ask at the parts place. I have been told that if one belt snaps it will tangle with the others and then break them.
The day I brought my bus home I had three brand new belts break. After fiddleing with everything I found out that Gates had put out a bad batch of belts!!! That was 7 years ago and I have not replaced a belt since.

[buswarrior]

Hello Richard.

Your big alternator equipped with grease fittings?

Belt drive, air cooled big Delcos need to be greased, pipe with zerk on end threaded in, in two places.

On new install, pre-load the pipes with grease prior to install, and go easy on how much grease you pump in. Once primed, my alt guy said a pump or two when you grease the rest of the chassis.

Too much grease just goobs out inside the alt and hinders cooling, leading to early failure.

happy coaching!
buswarrior