Seat goes forward, but not back word.
Checked voltage where wires plug into motor.
Good voltage (13v)
polarity switches back and forth with factory switch, but seat only travels forward.

Here's where it gets confusing.
If I physically swap the wires at the motor (removing wires from plug) the seat will travel both forward and back. (switch in the forward position, just swapping the wires at the motor)

This makes no sense to me since that is exactly what the factory switch is doing!

Any explanations?

 

If swapping the wires fixed it, I would think a connection was the issue. I have pulled the switches out of mine and completely dismantled them to polish the contacts with emery cloth. Now it works like a charm.

I can't remember how they ground, but the circuit in the switch may also reverse the ground and could be the culprit.

 

Yup, the switch doe s swap the ground too, but according to my meter I have good voltage on both positions.
Of course that's not under load, so I suppose it could be a poor connection.

Was it difficult to open up and clean off the switches?