Brodie

Take the cover off the motor housing and check the nylon gears that drive the motor shaft. I just replaced mine as a lot of the teeth were worn out. You can buy a kit from Sears Direct but I just replaced the whole thing as it was 30 years old and you had to take the old one out to repair it anyway.

Push it up and jam a rubber wedge shape door stop between the window and window sill inside.