![run 8 train simulator sd90 run 8 train simulator sd90](http://i.ytimg.com/vi/yvtUbRkH9mY/hqdefault.jpg)
It's also possible that the way the factory board is wired, it runs the correct direction on DC, but rip that out and put a decoder in (or bypass it, as many plug-in decoder installations do) and it might run the other way.
![run 8 train simulator sd90 run 8 train simulator sd90](https://2.bp.blogspot.com/-qdB_prqI6pQ/WFAQ69qLL1I/AAAAAAAAAmM/iwtCLACbIcQIColbbq9cyHsFqvqCoubKACLcB/s1600/screeny_2016.12.13%2B08.43.09.png)
If it moves the opposite way you expect, then the motor wires need to be reversed, and orange will connect to grey, and grey to orange. NMRA standard is the right side rail is positive for forward, so for north american locos, if the rail on the engineer's side is positive, the loco should move towards what should be the proper front. Only way to prove that out is to test on DC, and check your polarity on the rails. But an end cab switcher - that's just silly to have it backwards. I'm amazed they got the decals correct, even if it does run the wrong way. Understandable that it might be opposite what you want when invoilving a loco that ran either end forward depending on the practives of the prototype, good luck having a manufacturer change the wiring to that level of detail, considering the chassis might not even be made in the same factory as the shells. Once removed, it's pretty obvious which wires come from the left side of the trucks, which come from the right side, and which go to the motor. It's not difficult, especially if there already are wires running to that factory board. Since I always replace light bulbs with LEDs - it's just easier to rip it all out and run wires to the proper location. After cutting the required traces, only 1 of those big dropping resistors is actually in the circuit. I drew out the schematic on one of those by following the traces.
![run 8 train simulator sd90 run 8 train simulator sd90](https://i.ytimg.com/vi/XXgMxTh0Ko4/maxresdefault.jpg)
Particularly those P2K ones witht he big resistors and the traces marked with an X to cut when switching to DCC. I always rip out factory boards, because after attempting to analyze them and see what goes where, they are mostly a cluster you-know-what.