1999 f350 killing wiper motors! Any idea why?

[Kyle w]

One of my snow plow trucks is a 1999 f350 with the 7.3 and I have now gone through 3 wiper motors in the past 6 months. The factory ford motor and two napa wiper motors have gone bad. Any ideas where I should to find what else is wrong that is killing these motors or him I just getting bad motors? Every time it seems like the motor wants to turn the wipers and sometimes makes them rotate and if I leave the wipers on and pull on the wiper arm alittle it will go and sometimes set back to position like they should when off but wont start to raise again.
Any ideas are great! Thanks much!

[RIVER-RAT]

My first thought is an electrical short, I'd be checking every wire that has ANYTHING to do with the wiper motor...that's what I'd check..

[ttyR2]

Or...the bearings and pivots are binding and overworking the motors.