My wipers work properly when turned on. Turning them off is the problem. Intermittently they will refuse to park and a really annoying buzz comes from under the dash. Is there a relay or something for the parking mechanism?
Replace the motor...
Ill give it a shot, I just wasn't sure if the parking mechanism was on a separate relay like it is on some cars.
Had this exact problem on my first car. It was the motor. You could try taking it apart and cleaning the contacts.
I have had the exact same problem cleared it by cleaning the earth connection on the wiper motor hope this helps
Could be the park mechanism, could be the wiper motor governor. Neither is fun to fix. I've got a few spare wiper assemblies with bad park mechanisms that I've never gotten around to fixing. It's sometimes just easier to throw in a different wiper assembly and hope that it's better.
See here for more info:
https://www.coolcats.net/help/wipers.html