I don't know your exact situation, but I can tell you that if you don't have a good ground, even running a hot wire from the battery to troubleshoot won't work. This was my problem. I ran a jumper wire and nothing. I assumed the motor was bad, bought a new one, put it in and it wouldn't work either.
Then I knew I had a problem. I ran a ground and hot wire to the loose (uninstalled) motor and it ran. The problem was I had no ground to complete the circuit.
You can check continuity of your ground with a multimeter. The rubber mounting bushings have a metal sleeve that give the ground. Mine had dry rotted, shifted and thus the motor lost it's ground. It was a simple fix. Hope it's a simple problem!!
Matt B.