GP40 runs in opposite direction as other locomotives?

[NorfolkAndWestern578]

I recently got a Bachmann GP40 (in Conrail scheme) second hand from someone. When I took it home, it ran fine, but I noticed that it goes in the opposite direction as what the transformer is pointed to. I opened it up, took a look inside and cleaned it and greased it, and thought the problem would have been solved. But when I tried to use it as a helper locomotive on a freight, the problem persisted. While one locomotive was pulling towards the right direction (the one the transformer was set to), the GP40 was pulling in the opposite direction.

Can anyone tell me if there's anything I can do to make it run in the right direction? I know I can just send it in to Bachmann but money's a bit tight right now and I'd rather do any repairs myself. Thanks if anyone can help!

[David Leonard]

I don't know the insides of this loco, but if possible, turn the motor upside down in the motor mount. That will reverse the polarity.

[Joe Satnik]

Dear NAW,

David probably knows more about the Bachmann N Scale GP-40 chassis than I do, but..

if the motor recieves its electrical power through 2 wires to 2 motor terminals,

simply clip, swap (with each other), strip and re-solder the 2 wires (usually red and black) leading to the motor.

The following is the NMRA standard S-9 for direction and polarity:

...." Positive potential (a.k.a voltage) applied to the right hand rail shall produce forward motion.  

The term "right hand rail" as used herein means the rail to the right of the observer standing between the rails

with their back to the front of the locomotive. "........

(Now if I can only figure out how to shrink myself to stand between N-Scale rails.....)

Hope this helps.

Sincerely,

Joe Satnik

[David Leonard]

Actually I don't know for sure anything about the GP40. If the motor is in a plastic motor mount and makes contact with tabs in that position (like is Atlas models) and can be removed without having to cut any wires, then turning the motor upside down will reverse the polarity. But if the wire contacts go directly to the motor itself, then Joe's suggestion is the only solution. If you can't tell from observation what the electrical setup is, then just go with Joe's method.

[seadowns]

Hi!
AFAIK is the GP40 similar to GP50 and U-23B. There's no wiring whatsoever, simply pull the shell, unscrew the two body screws, lift off the upper  body halve, turn the motor 180° and place it back in the body, so the two motor contacts meet their contact points again. Carefully set the trucks in and keep an eye on the two semi-circle brass contacts outside the body slots and the plastic spacers between body halves. Push the lamps back in and that was it.
The loco will now run in correct direction.
With a little skill in tinkering the most of this is self-explanatory while working on it.

Regards
Mathi