OK, I'm bad, this isn't for a Truck, but it is a GM. The pass window in my wifes '90 Cierra stopped working last fall. So with nice weather, I took motor out and tried two other known good ones, but no dice. So I checked for power, and one wire lights up both switch positions, and the other, (prob down) only one way. Tried wiggling drivers harness, and nothing. So how do I diagnose this? Prob a broken wire in drivers door rubber accordian, where they always break.