I have a Whirlpool refrig model ET186KXFW0 1 manufactured in 1997. The freezer started frosting up about 2 months ago. I defrosted it but it's frosting up again.
How do I fix this?

Tom

Check you defrost coil and timer. The coil you can test for continuity and you can manuelly advance timer to see if it's working, Also listen to be sure the timer motor is working. While your'e at it, clean the condensing coils an motor. Once they get dirt build up on them, it will affect how the unit is cooling

Your defrost timer is shot. Had the same fridge and mine did the same thing until I got a new defrost timer.

Twinkieddoter, You may be right however I never condem a part without first testing. Doing that can just be a lot of money on parts without the repair.