When you press the window switch, what happens? Do you hear the motor trying to roll down the window? If so, the exact thing happened on my drivers window. I just used some PB Blaster penetrant to get everything lubed up and then greased all the runners with white lithium grease. Window still works perfectly 7 months later. If you have determined that the window motor is not getting power, than you have to work backwards thru the wiring to find the problem. Do you have power at the switch?? If so maybe there is a break in the wire at the door jamb where the wires come thru. A 12 volt test light is indispensible in this situation.

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Orland Park, IL
1985 300SD 215,000 miles