finding positive and negative on locomotive motor

[Anonymous]

I am attempting to put a decoder into a locomotive from a Walthers Trainline set. It doesn't have a lightboard or anything like that, so it needs to be hard wired in. My question is how do you find positive and negative on the motor. I need to be able to wire the decoder in and I am not sure which is which. Or does it matter. I think the only thing that will happen to it is the loco won't run the right direction. Also another thing while I have your attention, when they say right side rail, is it right side while looking at the back of the train or the front? Thank you in advance for any answers or any tips on how to wire decoder into this loco.

[jfugate]

If the loco is wired like most modern locos, the red wire is the positive one.

If both wires are the same color, and you really want to do it right, get some test leads and test it out. Hook the red and black decoder wires with test leads to the rail, then connect the orange wire to one loco motor lead, and the gray wire to the other motor lead.

Dial up address 3 on your throttle, set the direction to forward, and see if the loco moves forward. If so, congratulations -- mark the motor lead that's connected to the orange side and when you install the decoder wire it up that way.

If the loco runs backwards, swap the orange and gray wires to the opposite motor leads -- things should run forward then.

It's not the end of the world if you do happen to wire it in backwards. You can use bit 1 in CV29 to flip the direction electronically in the deocoder. If the loco is running backwards, just add 1 to whatever value is in CV29 and the loco will run the other direction.

[cacole]

Assuming that the loco has a can motor, normal wiring protocol would be for the negative wire to be on the bottom and positive on top, or negative on the left and positive on the right, looking at the rear of the motor. If the motor runs backwards, you can change its direction of travel with CV29 instead of having to change the wiring.

[Fergmiester]

Assuming you've got power to your loco, take your tongue and bridge the shiny stuff. If you get a good jolt, chances are you've found both + and -.

The other posts are just the fancy way!

[:D]

[rrinker]

I don't know what kind of Trainline loco is involved here, but I have a pair of FA's and color code? I don't think they ever heard of color code. I'm kind of suprised it even runs, as the copper traces on the included circuit board are questionable at best. But it all goes away fro DCC installation anyway.
NMRA standard says the right rail is positive for forward movement. So whichever motor terminal the pickups from the right (engineer's) side of the loco are connected to should be the positive terminal for the orange decoder wire. If you hook it up the wrong way, it will just run backwards, no damage will occur to the loco or the decoder.

--Randy

[Anonymous]

Thanks for the help. I finished wiring my loco and I got the positive and negative right the first time. The loco runs but not very smoothly so I need to do some more work on it.