Most models have a relay between the switch and the motor...get a hold of a wiring diagram and see if yours does too and examine it. It could also be a broken wire in the door hinge joint. Try activating the switch while opening and closing the door.

You should be able to see if the motor is getting power if you pull off the door panel and test with a volt meter at the wires while activating the switch. If it is you know it is the motor, if not it is in the wiring to the motor. This isn't all that hard to track down.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz