M8000 motor assembly: Don't do this

[Zorba]

Keeping this short and sweet, dumb mistake on my part that if I'd been paying attention, I "probably" wouldn't have made. Recently cleaned, painted, etc, M8000 motor wouldn't run in either direction, not even when bypassing the solenoids. The key word is "painted"...

If I'd been paying attention, I would have noticed that there was no bonding strap, wire, bolt, or screw to ground the frame of the brush holder assy to the body of the motor. So painting this end is NOT a good idea...

Had to dis-assemble, scrape and sand off the paint - now the motor runs just fine. This method of assy reminds me of guys who don't run a separate ground wire to their trailers, but instead rely on the hitch ball to provide ground - in other words, not the best practice, but it is what it is, and now I know - and so do you!

Once re-assembled, THEN I put a touch-up coat of paint on the junction between the endcap and the motor body to prevent rust...

 

[motomick76]

Instantly reminds me of when I worked on wind turbines. Replaced a generator, and turbine ran great for 3 months. Then it would randomly fault on generator speed issues. There is a rpm sensor just like one that is found on our Jeeps that measure crank rpm. Tried everything we know for 6 months. Got a electrical engineer out to measure wave form from sensor. Since it is DC, it should be a square on/off waveform. It was not square, but sporadic. The sensor is ground through the housing, to the bracket, to generator. There was pant on bracket and where bracket bolted to gen. Scrape paint off both - problem fixed. So many electrical issues are result of bad grounds/neutrals. Great find!

 

[Zorba]

Instantly reminds me of when I worked on wind turbines. Replaced a generator, and turbine ran great for 3 months. Then it would randomly fault on generator speed issues. There is a rpm sensor just like one that is found on our Jeeps that measure crank rpm. Tried everything we know for 6 months. Got a electrical engineer out to measure wave form from sensor. Since it is DC, it should be a square on/off waveform. It was not square, but sporadic. The sensor is ground through the housing, to the bracket, to generator. There was pant on bracket and where bracket bolted to gen. Scrape paint off both - problem fixed. So many electrical issues are result of bad grounds/neutrals. Great find!

I knew I couldn't have fucked it up too bad - it was obvious once I really took a look at the brush assy - oh, these other two go to ground... Uh, how do they get there... Well, DUH!

I would have liked to have seen a positive ground connection rather than a pressure fit scenario, but it works like most things do once one understands them.

Your story in turn reminds me, for some reason, of a computer problem I had in tech school with a micro-computer that I had wire-wrapped. Darn software showed every appearance of being intermittent. Instructor thought it was my software - after staring at the code for a couple of days, I figured out that that couldn't be it, and started poking around with an oscilloscope. Clock signal was all over the place - bad connection at the crystal. Hit it with a soldering iron and the world lit up! "No such thing as intermittent software" has been a catchphrase of mine ever since!

 

[motomick76]

Those hard lessons are some of the best lessons, we never forget, and we always check!

 

[Zorba]

And, just for fun:

 

[Blackjack]

Do yourself a favor and smear some sealer (I use Ultra Black) on that joint of the brush cap to motor case. You can also do the motor case to the drum support just make sure to not block the drain slot.

 

[Modoc Guy]

Good thing to know for future reference.

 

[Zorba]

Do yourself a favor and smear some sealer (I use Ultra Black) on that joint of the brush cap to motor case. You can also do the motor case to the drum support just make sure to not block the drain slot.

That's precisely my plan!