Just happened to me, so this is what I did....Could be one of four things, First was there something jammed in window,( probably not, but you got to ask) something that could have jammed the regulator? 2nd, check the relay, if your moon roof, radio and wing windows still work, its not the regulator, because they are all on the same relay. 3rd, do you hear the motor running? If so your regulator is bad(the actual scissor arms that move the window up and down) 4th and finally, if all that checks out, you need a new motor, make sure you get the right one for which ever window it may be, not bad in cost, between 60-80 dollars depending where you buy it. Hope I helped!
