Get in van turn headlights and key on,do not start leave door open so dome light stays on, try to raise the pass. window and watch dome light very closely at the same time as trying the window, see the light dim just a little bit. Try it again see it dim, now try the same with the drivers window see it dim if it does replace window lift assem. if it does not replace switch Or find open circuit to switch. Headlights just adds a little more load so you can see the light dim. Works every time.