I have a 1993 gmc safari. The front left window driver side will roll down about 4 inches then it makes a grinding noise. Same if i roll it up. It has never went lower then 4 inches. Today my right front windoe stoped working all together. About a week ago i noticed if door was open the passenger window would not roll down. But if u shut the door it would. Then today nothing. Checked the switch it good. Help. Where can i get motor regulator for both sides cheap.?