Product review (5 stars): Whirlpool Part Number W10225581: BI-METAL DEFROST
I was bummed when my refrigerator stopped blowing cold air. My freezer was freezing still, but it was also accumulating a lot of frost and ice even though it wasn't supposed to. After reading some forum posts and watching a couple Youtube videos, I decided to order the BI-METAL DEFROST  part and replace the bad one myself. When I opened the package and the part didn't match exactly (small shape and size variation), I got nervous, but forged on and decided to make the swap. Surprisingly, the swap went smoothly as demonstrated on the Youtube videos. It has been about 3 weeks since I replaced the part and there is no more icing/frosting in the freezer and the refrigerator side is nice and cold. NOTE: There are no instructions. Only the part is shipped. Just search for "Refrigerator Defrost Thermostat (part #W10225581)-How To Replace" on Youtube and you'll see how straight forward the installation is.