Windshield wipers wont shut off

The problem is in the wiper motor assembly. Did you ever notice that when you switch the wipers off they always go back to the home position? This is due to a switch that keeps the wiper motor operating until the wipers are parked. In many older GM vehicles this is accomplished with a leaf type switch which opens when the wipers are in the correct position. when the dash switch is turned on this switched is bypassed keeping them on-when the wipers are turned off the motor continues to operate until this connection is broken.

Inside the wiper motor housing there is a nylon gear that drives a cam that cycles the leaf switch-most likely the gear has become damaged so it no longer drives the leaf switch allowing the switch to remain closed. A cheap fix is to disassemble the motor unit and piece of tape between the contacts. Although the wiper will not park properly they once again can be controlled by the dashboard switch.

In later vehicles the wiper position is located with an electronic sensor with a small PB board - the repair of this gizmo is beyond the scope of most shade tree mecahnics - so the solution is to replace the entire wiper motor assembly - unfortuneatly.

Try adding a ground wire, just take a wire and rub it on the motor ad the other end to ground on battery. i find alot off problems are caused by bad body grounds or on gm wiper motors the internal ground goes bad. grounds are one of the biggest problems in electrical systems on all trucks and cars.