My 93 Winnie Vectra on a Spartan chassis with Cummins 5.9 is about to get its 3rd or 4th alternator in 70 kmiles. It had already failed when we bought the rig and the shop that replaced it had to cut the fan off the alternator to clear the belt tensioner. They said not to worry, there was no fan on the alternator they removed. Both alternators had failures of the internal regulator and are/were overcharging. The present alternator intermittently exceeds 18 V.Here's what I know:1. Neither alternator had a fan2. Cummins shows that my ESN should have a Delco 15SI alternator, which is apparently what I have3. Delco 15SI comes with a fan4. As near as I can tell, the alternator brackets look like those pictured on Cummins web site for my ESN5. The space between the alternator and the the radiator fan pulley is so small that the belt tensioner overlaps the alternator body, so there is no room for a fan.I can't imagine that Cummins sent an engine package to Spartan without a fan on the alternator. Have others had this same experience and/or found the fan cut off their alternator? I'm not enthusiastic about replacing the alternator every 10-15 k miles.thanksGary

If the alternator came from the factory with a fan, it probably needs one.....time to call Spartan, then Cummins.

The alternator sits on the engine backwards to receive cool air.It gets heat from the engine on it's backside through the opening where the regulator etc are.I replaced mine at: 16,541 miles for under 12 AMP charging54,987 miles for under 12 AMP charging put a 160 AMP on88,921 miles for over charging 16 + AMP's replaced with a Delco 22SI 150 AMPSo I am getting 34-38K miles between alternator's.

Triker I think you mean Volts not ampsUnder 12vOver 16v

-Could someone have done a MacGyver fix years ago and changed out the tensioner or it's bracket with the wrong one? -Could another tensioner bracket be used to move the tensioner out or the way? -Could a longer belt be used to allow the alternator to rotate farther away and clear the tensioner?That motor was used in a lot of applications and there could be dozens of tensioner/braket configurations.

DSDP Don wrote:-Could someone have done a MacGyver fix years ago and changed out the tensioner or it's bracket with the wrong one? -Could another tensioner bracket be used to move the tensioner out or the way? -Could a longer belt be used to allow the alternator to rotate farther away and clear the tensioner?That motor was used in a lot of applications and there could be dozens of tensioner/braket configurations.DonIf there's something that wasn't per Cummins, I think it would have been Spartan. For awhile, I thought that maybe Spartan had moved the alternator to accommodate a narrow frame or other reason, but there is plenty of room there.The tensioner pulley itself is the interference. It sits between the alternator and fan pulleys. Moving the tensioner pulley would change the belt tension. I don't see another location where the tensioner would fit.The longer belt suggestion is a possibility. The alternator location is fixed by the brackets (3 mounting points --> not rotatable), but a longer belt will rotate the tensioner closer to the radiator fan pulley and further from the alternator. There is not much room towards the radiator fan pulley either, looks like less than 1 inch. But I've looked at the Gates belt chart, and the lengths near my 'original' are in about 1/2" steps, so I might be able to find one that places the tensioner in an OK spot. So far this has seemed like my best option, though I worry that if the belt stretches with age, does the tensioner pulley then contact the radiator fan pulley...You are certainly right about the variety of applications. One nice feature to Cummins is that the ESN is supposed to determine the configuration. As near as I can tell, everything I can see looks like what Cummins shows for my ESN. Perhaps I could find another configuration that would allow an alternator fan, but rather than chasing down other brackets, I'd just put spacers under my present alternator brackets. This is probably the best way to go, so long as the bolts come out without breaking ...thanksGary

cummins 6b5.9 alternator failures | Good Sam Community

dsr27
Explorer
May 15, 2016
sjholt wrote:
Don't worry about the bouncing of the idler pulley.
with 3 changes of belts, every one bounced the pulley about.
I even changed the whole idler arm and pulley and it still did the same.
I don't think all the belts are perfect.

this is reassuring, since we have the same motor. I too tried the tensioner change to no avail.

Thanks
Gary
dsr27
Explorer
May 15, 2016
MrWizard wrote:

you could go buy the 'soft' belt an install it

yup ... I did try the 'soft' belt. That's why the 1st video has a green belt (HD) and the 1200 rpm video has a black belt (standard, both are Gates). There was no difference in the bounce. And comparing the belts in my hands, I couldn't tell all that much difference between them before I installed the black one, so I wasn't surprised the bouncing was the same.

It's probably done this for 70 kmi. I certainly never looked before. That would be testimony to the quality of the original tensioner. As far as I can tell the original shows no signs of wear. I would put it back on were I not so lazy.

thanks
Gary
MrWizard
Moderator
May 15, 2016
looks good to me
you could go buy the 'soft' belt an install it

torsion would not be needed in the idler, IF they never bounced
i think what you see is normal and with in the proper specs
sjholt
Explorer
May 15, 2016
Don't worry about the bouncing of the idler pulley.
with 3 changes of belts, every one bounced the pulley about.
I even changed the whole idler arm and pulley and it still did the same.
I don't think all the belts are perfect.
dsr27
Explorer
May 15, 2016
beginning to wonder if this isn't normal for the older 6BT. There is a lot of info about torsional vibrations in the 6BT. I know that ours vibrates the house quite a bit at idle and then smooths out at road speed. The same thing happens with the tensioner bounce. By 1200 rpm it is much calmer. Video frame rate isn't really fast enough for this, but visually (to the eye) it's much calmer

1200 rpm video
Kidoo
Explorer
May 12, 2016
I don't know if yours is like mine but if you want to take a good look at everything. If this can help, my intercooler is very easy to remove and it gets you access to the back of the engine. I remove the two top hoses, unbolt and pull the hydraulic revervoir out of the way, disconnect and plug the transmission hose, 3 bolts on the cooler, pull up on the cooler as there is a lip on top and pull the cooler out. Then I remove the for bolts on the fan and pull the fan out.
dsr27
Explorer
May 12, 2016
Wolfe - I haven't seen any obvious run-out yet. You can see every pulley in the system in the video, except the crank pulley/harmonic damper.

I have seen some reference to harmonic damper failures causing this, so I looked at Cummins service manual for inspection tips and mine looks fine. Note that on the older Cummins the pulley is the outer 'ring' of the harmonic damper, so wont have run-out unless the damper has failed. Even though mine looks OK, the rubber is 23 years old. I'm not ready to replace that on spec, at least not yet.

I'll look more carefully for run-out, that is a good suggestion.

thanks
Gary
wolfe10
Explorer
May 12, 2016
Look at the other pulleys driven by that belt. Likely something is out of round/not center mounted.

Have often seen this on bolt on pulleys on the harmonic balancer. Some of those pulleys have enough play in the mounting holes that you can slightly move them around.

Tape a piece of chalk to a stick and with the engine at idle, slowly move it toward a pulley that has run-out. Stop when it first marks the pulley. With engine off, usually belt off, slightly shift the pulley away from the chalk mark.
dsr27
Explorer
May 12, 2016
well... new tensioner didn't help with the bounce:

bouncing video

or:
http://vid1208.photobucket.com/albums/cc364/dsr27/MVI_2236_zps850jccg8.mp4
Kidoo
Explorer
May 11, 2016
Mine is a Prestolite 160 amp, J180 mounting in a cummins 300 HP 2003, see below. I had it rebuilt and the guy told me not to charge dead batteries with the alternator as it will overheat, the diode where toasted. He said if your batteries are low to recharge them with the gererator or shore power before starting the engine, this will save the alternator.

http://www.prestolite.com/pgs_products/specs.php?item_detail_id=25083&item=8LHA2071VA

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