Trouble with wiper motor

Year? 2 speed? 3 speed? variable speed?

There's a check out procedure in the shop manuals. These have a rather tricky wiring scheme. MAKE SURE the switch is grounded!!!


The wiper motor is in my 74 Duster and it is the 2 speed. It was working 12 months ago, but has not been used since then. I was checking it before its annual safety inspection and the wipers did not work. I turned them on and at the same time pulled on the arm and it did move under its own power for a few inches and stopped.

Could it be dirty brushes in the motor? Can they be serviced while still in the car?