I had a similar problem with my 94 Lumina Van. The problem was in the wiring which is inside the rubber housing on the driver side door between the frame of the vehicle and the door. There was a short in one of the wires which I simply soldiered back into place. Take an exacto knife and carefully separate the rubber housing, not to touch any of the wires inside. Once you're able to see all the wires check for a short, fix it and close the rubber housing using duct tape.
