GE U36B Diesel only runs when one set of wheels are on track

[jman76]

Full disclosure, I'm not an aficionado by any means.   I have an old Bachmann HO set I had as a kid.  it's been boxed up for close to 30 years and decided to take it out to show my kids.   I have a GE U36B Diesel that sorta doesn't run.    Voltmeter shows tracks are getting power but the odd thing is this:   The train has two trucks that holds two sets of wheels each and the drive wheels move only one of the trucks are on the rails, doesn't matter which one is on tracks but as soon as both trucks are on the tracks the wheels stop and voltmeter shows no power on the tracks which to me points to a short somewhere, but since the trucks independently power the wheels I'm not sure where that could be.   Any suggestions on where to look would be appreciated. 

[Flare]

It sounds to me like one of the trucks is backwards.  See if one can be turned 180 degrees without putting too much strain on any wires.

[jman76]

It sounds to me like one of the trucks is backwards.  See if one can be turned 180 degrees without putting too much strain on any wires.

Thanks for the response, unfortunately for this model that's not possible to rotate it like that because the couplings are part of the truck.

[Len]

Sounds like the wires on one of the trucks got reversed. It may have been disassembled "back when" and when it was put back together the wipers on one truck got reversed. With the shell off, you should be able to see how to drop a truck out. Then it should be fairly straight forward to swap the wired wipers around.

Just do this to one truck, and you should be good to go.

Len

[jman76]

Thank you both for your help.     When I gaining access to the wiring I found out how to take the bottom cover of the truck off, which also had the coupling on it so I was able to rotate the whole thing and once I put it back to together it work normally!!!

My guess was many moons ago I probably took the cover off to either make it easier to put on the rubber traction band on the wheels or, since I was a kid, just took it apart to see how it works.      

Anyway...thanks again!!