My Amana refrig. evaporator keeps freezing up. The refrig. section has little to no cold air coming out of it. I defrosted the evap. with a hair dryer it lasted for a little while but the ice came back. At this time the refrige. was working correctly. I was looking into the defrost control located in the uppersection of the refrig. but not sure if its working correctly. What would my problem be?? Thank you for reading my post hope you can help.