My vent window won't stay open...

I've got to get into my doors to lube the locks and window tracks, and I might as well fix the vent. The driver's one won't stay open; is there a spring inside that performs that job? I've never torn the door apart on one of these.
My Mazdas pulled up out the top after I unbolted a few channel screws and a support bolt all the way on the bottom of the door. Access was easy with inner panel popped off.