I would first get the battery out and clean all the corrosion from under the battery compartment, replace any power cables that seem to have been sitting in the corrosion, and check to insure all the cables or in their correct locations. you may have a power cable in the wrong spot, or so much corrosion that it can carry enough power to turn the motor, but my bet is cables on the controller wrong. bad contact tips would never cause this, you would get a code rather than try and run.

I would be thinking contactor tips
either rebuild contactor or replace