The windshield wipers on my 1995 GMC Suburban were haunted. After a trip to Savanna and doing the ghost tour, the wipers took on a mind of their own.
If I tried to pulse them them would run several cycles before stopping. On intermittent they would run ad few strokes then stop in random positions.
In mist they would often just run on and on until I considered pulling the fuse. They they might stop in a random position rather than parking at the bottom of the windshield. A few miles down the road they would decide to park.
I was ready for an exorcism. However every time I put the truck in the shop to see what was wrong the wipers would function perfectly. Haunted.
Recently on the way home from Atlanta in a misty rain, they continued to act up until I got back to the shop. I now had my chance to find the trouble.
It turns out the park signal is generated inside the wiper motor. I watched a few youtube videos to see how to remove the wiper motor. It is not too bad.
Just remove the wiper arms, a few screws (some of which are hidden) and remove the grill over the wiper motor.
You might want to mark the position of the wiper arms on the motor as they adjust where they are connected. Loosen the ten mm head bolts and slide the wiper arms off the motor drive.
Then remove the three bolts that hold the wiper motor to the firewall. Disconnect the wire and you can take it out of the truck.
Before replacing the motor, I wanted to know why it did not work. I removed the cover and found a circuit board inside. The board shows signs of being hot and possible smoke removal.
I did a quick search and found the board was available separately. I ordered one form my local parts store and proceeded to put everything back together.
I found the board can be swapped without pulling the motor off the firewall by simply removing three torx screws. I swapped the board and now the wipers stop when turned off. The pulse and intermittent settings work as expected as well. Exorcism complete.