Its probably the switch. The contacts burn from arcing. The easy way to check is to switch the drivers wires to a known working switch. There are no microswitches that turn the motor off. If you have a voltmeter you can see the motors draw down the voltage when they are jammed at the end of the window travel. If it is the switch they are pretty easy to clean. Just pry them apart carefully taking note of where the parts came from. One you open the switch you will see the blackened contacts. I shine them up with emery paper.