Front window motor only runs when lights on

[ps2cho]

This is the drivers side only on my '87 260E.

Its a weird one...If the lights are off, there is no power to the motor. If the lights are on, I can hear the motor in the door, but the window does not roll down.

I swapped the switch with the passenger side one and no luck. The front passenger window is the only one that works in the car. I have replaced all the fuses in the fusebox too.

Any ideas?