To make it go backward, I would connect MOTOR+->GND and MOTOR-->12V .

I have 2 relays with 3 pins each. Each relay can reswitch one thing to one of two other things when switched.

The currently relay has ground, so I could make it wire ground to MOTOR+ when the other way.

Then the other relay would have 12V, and could wire it to either MOTOR+ or MOTOR- .

But, in that arrangement there would be no way to turn the motor off.

Maybe it makes more sense to undo the wires and move them by hand.

I'm thinking that I will need to do this again, though. But, it's easier to be physically near the motor when sending it in reverse.