Just assuming it’s not a simple fix based on the symptoms.


8kw powertech with CAT engine. Over 3000 hours. Got back after a pass, no power inside coach. Went around to the generator cabinet and could tell something was seriously wrong before I open the cabinet door.

Noticeable but not overpowering electrical fire odor.

Rotational failure noise. Hard to describe but wasn’t pleasant.

Breakers on the unit were not tripped.

I will pull some covers off and fire it back up tomorrow depending on what I see inside. What’s the chances I can take this somewhere and get it fixed for less than the cost of a small house??

Generator end bearing failed and allowed rotor to hit stator possibly. Would need the complete generator end/barrel replaced. Powertech sells everything usually to fix them and has a website with all parts shown and prices. They are in Florida.

I’ve fixed a number of them. Usually brushes and slip rings fail and voltage regulators. Fan drive and engine service work as well. They are good units and worth fixing vs what a new one costs.

Thanks. I think I found the parts on their website. 1-10 how hard would the repair be to do myself?? Any special tools I need to make or buy?

Replacing a complete generator end barrel is fairly complicated but not for me.

Remove a lot of stuff and a lot of wiring.

About like changing a transmission but with a lot more wiring and other stuff to get out of the way
Do it wrong and you’ll wish you paid someone who knew what they are doing to fix it.

Mostly just a lot of nut and bolt work and mark wiring.

They have wire diagrams on their site and that’s a big help if you can understand what your looking at.

If no than you have a lot tougher time doing the job.

This message has been edited. Last edited by: SCDIV1,

Got the case about half way off inside the compartment. Fired it for a couple seconds. Your diagnosis sounds about right even though I can’t really see much.

Looks pretty easy to swing the genset around so the motor is hanging out of the compartment. This leaves most connections on the outside of the set in place. I’ll put some cribbing outside to slide the genset onto. Then probably hang the motor itself from my loader tractor before I unbolt if it’s too heavy to just manhandle (guessing under 200 lbs so tempted to just 2 man pick it if that’s right).

Wires appear to be labeled but haven’t got my head in there all the way to read anything. I think I’ll get the new one here and see if I can match wires.

Also, a little over 4000 hours, not 3000 like I originally posted. Hopefully it’s still worth it??? I never noticed the inspection cover is missing from under the motor so the inside of the motor was basically exposed to the road. Wonder if that had any part in the failure?

Marathon Pancake model 640822. If anybody knows a better source than Powertech, let me know.

When I work on a machine I'm not familiar with I take some pictures with my Iphone.

I also will take the extra time to mark all wires for what they are and where they go...

A little extra time before taking something apart can save a lot of time later on...

Thanks for all the help! I did just as you suggested, pictures plus made my own schematic (the ones from powertech seemed incomplete or at least not all info on the same sheet).

Harder than it looked at first but not that bad I guess. I had to cut the case a little to keep from having to completely remove the unit from the coach.

Worst part was trying to get the flywheel bolts out before i found out I could just slide the outer housing off the rotor.

We made it to the racetrack and have about 8 hours on it already so I think I’ll call it a success.

Seems like the old unit could be fixed. I Considered repair instead of replace but didn’t want to blow the race season screwing with the genset. It destroyed the brush housing but no obvious damage to rotor or stator (comm maybe a little chewed up). I don’t think it spun the bearing in the housing, the bearing was just disentegrated. Any thoughts on what I could do with it (sell as core, fix and sell, etc..)?

Really no market for used parts like that as far as I know...

If there are no rub marks on either the rotor or stator they are likely good.

Only tests that can be done is with an ohm meter and that's not totally conclusive but is usually a good indicator of good or bad. A "megger" is the conclusive test on stators. It sends a high voltage thru the windings to try and find leakage. They develop turn to turn shorts.....Seen it many times on Onans. Stator just burns up and kills other parts when it does....

PowerTechs often wear out the brush rig pretty bad and end up damaging the slip rings. That part is replaceable on some of them and not easy to change. I've done a few and helped someone else do one over the phone.....

I almost always remove machines for major repairs....

Diesels often will do exactly what you found....The engine transmits a lot of hammering vibrations thru the rotor.....bearings and end plates get beat up...

I repaired a Miller Diesel Trailblazer a few years ago for this issue and it turned into a nightmare of a job.....Complications and many parts trashed....I fixed it but it was tough and not the only machine that gave me fits trying to fix....