I had that happen as well. I was driving in heavy rain. Two problems occurred at the
same time. I couldn't turn off the wipers and whenever I put the turn signal lights on the cruise would dis-engage. After a search on the internet, others had found the problem was moisture had got into the wiper motor connector. I later un-pluged the connector, dried it, applied dielectric grease, re-connected then taped up the connector with electricians tape, then located the connector higher up to a drier location in the engine bay. Neither of these problems occurred again, this was 3 + years ago.
Ellen & Greg
08 National Dolphin DL-35Ci, RoadMaster Rear Sway Bar, Rear Trac Bar,
Workhorse W22, Kelderman Air Ride, Towing 08 Smart Car