I have been racking my brain to try to see how this could come about. Jeff's suggestion about the washer pump is a good one!
Micheal, please remove the washer from the motor and remove the electrical connections and re-test please.
So normally the park circuit find it's ground through the base of the motor/bolt/firewall. But there is an internal spring contact that when parked, removes the firewall ground path. For the park circuit to find the ground all the time would mean the contact is jammed and I would expect strange noises from the gear box.
I am leaning more to incorrect wiring. You performed the wiper motor using my bench test diagram, correct? https://www.camaros.net/forums/showth...per+bench+test
If the bench test is successful and the motor continues to move a partial turn to the park position (when you turn switch to off), then I would say the motor is good. If it does not
park normally in the bench test, something else is going on.
If the bench test is good, but still does not work correctly, I suspect the wiring to the switch and/or the ground plate wire not present.
But those really do not match the problem exactly
below are the "normal" problems
Not Parking: the ground path to the firewall not connected
Not working at all: switch or switch ground issues