how to test the windshield wiper motor in 2003 mercury grand marquis LS

99% of the time its not the motor. its in the switch itself on the steering wheel. get inside and shake the switch. switch it on and off fast. if that works then Great! if it still does not work, then unhook your battery for 30 minutes. after 30 minutes reconnect the battery and try it.

I agree. If you think about all the wear and tear it gets as a Turns Signal Switch, it's amazing that the Wiper switch lasts as long as it does. There are 2 fuses that operate the wiper system - one under the hood (Battery) and one under the dash (key power). Does the Washer work? High beams, turn signals and Hazard flashers too?

Replaced switch on steering wheel, it didn't change things, thats when I replaced the motor. Wipers worked fine for a few weeks, then stopped. I checked the replaced wiper motor with another new one, there is nothing wrong with it. Fuses are fine, washer works, lights work fine, hazard flashers work. Thanks for your help.

Thanks everyone for your help, the wiper motor was bad, had to replace it. Thanks again.

THE LIGHTS WERE FLICKERING THEN JUST HIGH BEEMS WOULD WORK THEN WIPERS WOULD GO ON WTHOUT PUTTING THEM ON THEN ON DAY CHECKED IN RAIN IF THEY WENT ON "WIPERS"THEY DID SO SHUT OFF THEN NEVER CAME BACK ON ....AND MAIN LIGHTS NEVER CAM BACK ON ....ALSO WPERS SOUNDED LIKE WINING A MONTH BEFORE THEY STOPPED

The probable part failure is the M83-4 framastam portminder.

Kiss my anterior aperture.