My neighbor has a garage kept 2002 mustang with 45,000 miles... on Friday he said his son was complaining about wiper problems so I went over to look at it and by then the wipers were not working at all. I probed the wiper motor harness and found 12v at the proper times on the proper pins. I replaced the motor and the wipers worked again. He just came by today and the wipers are moving very slow and weak (like they were before) and won't wipe all the way across unless you lift one of the wipers off the window. It's possible the new wiper motor is bad... but I'm also leaning towards the possibility of a bad switch since it looks just like the one in my Ranger which is bad as well. Has anybody heard of this? I was headed to the junkyard anyway tomorrow is there anything I should grab off a mustang to try swapping around?

 

Bound up wiper linkage would be my first guess, do the wipers move easily with the motor disconnected from the linkage ?

 

Yes, the linkage is fine.