Does the G scale Heisler have power pickup on all wheels? I am only able to get my Heisler (just bought used) to operate when I apply power leads to the front contacts. Nothing happens when I put the wire leads on the rear trucks. Any suggstions???
Sounds like you got a bad unit, mine picks up on all wheels.
Most likely, there is a broken wire or solder joint between the truck and the motor. You will have to field-strip the model to determine where the problem is.