Unusual Short Problem With PS-3 Engine

Weird makes no sense to me.  Once it get going it resolves?  G

Take the shell off.  It's likely one of the pcb's mounted low on the frame is shorting to the frame.  Put some electrical tape beneath the pcb's to eliminate the arcing.  If you don't resolve the issue you'll destroy the electronics in the engine.  All of my recent GP38's were doing this.

Clean the black off of the wheels.  Also replace the black screw that holds the ground wire to the trucks with a silver screw or remove the black coating.   There was a batch of these engines that had ground issues.  

Symptoms would be sparking wheels or arcing from the frame to the trucks.

I just put one back together with a seemingly identical issue.  It was the wire from the center track pickup chafing on the frame.  Amazingly, the sparks I saw seemed to emanate from all over around the truck, fooled me at first.  I bent the connection away from the frame and also added another heatshrink layer for insurance, all fixed.

@GGG posted:

Weird makes no sense to me.  Once it get going it resolves?  G

Ya, after an inch or two of reversing along the track, it stops shorting. I can run the engine indefinitely without the issue occurring again until I stop and change direction.

@MichRR714 posted:

Take the shell off.  It's likely one of the pcb's mounted low on the frame is shorting to the frame.  Put some electrical tape beneath the pcb's to eliminate the arcing.  If you don't resolve the issue you'll destroy the electronics in the engine.  All of my recent GP38's were doing this.

Not sure about that... None of the circuit boards are anywhere close to touching any part of the metal frame. I suppose it might be well hidden, or a damaged wire making intermittent contact somewhere, but there's nothing I can see.

@David Minarik posted:

Clean the black off of the wheels.  Also replace the black screw that holds the ground wire to the trucks with a silver screw or remove the black coating.   There was a batch of these engines that had ground issues.  

Symptoms would be sparking wheels or arcing from the frame to the trucks.

If this were the cause, wouldn't I have had this issue from when the engine was brand new all the way till now though? This is a new problem that has never happened before, which leads me to believe it is some new type of wear / damage on the inside that is causing it.

@gunrunnerjohn posted:

I just put one back together with a seemingly identical issue.  It was the wire from the center track pickup chafing on the frame.  Amazingly, the sparks I saw seemed to emanate from all over around the truck, fooled me at first.  I bent the connection away from the frame and also added another heatshrink layer for insurance, all fixed.

This sounds like a similar issue. I'll take a look at the two pickup roller wires. I've already had an issue with this engine in the past where internal wires were rubbing on the frame and causing shorts, however the symptoms were quite different than this time.

Is there anything I can do to help narrow down the issue? Unplugging / turning off certain things to see if the problem still persists?

It might be normal buildup on heavily coated wheels.  It doesn't cost anything to do this.  I would check out John's suggestion too.  

While you are in there, I would do both.

Most of what folks are saying would be constant while running.  This symptom that only shows up for a short period after changing direction sounds more like the flashback diode for the relay.  He has cleaned pickup and wheels according to his first post.  I would inspect the bottom of the board for any visible damaged component.  You could swap in another board if you had it and that would either eliminate the board as the issue or point to the board.  G