My 14 year old GE Profile evap coil in the freezer was frozen solid, and I found that the defrost mechanism was not functioning at all. There are three components--this timer, a defrost thermostat, and a defrost heater--and I wasn't positive which was bad so I did all three. I got the thermostat locally, only because it was out of stock here. You can read my heater review if you'd like. This timer was easily replaceable and was exactly the same as the stock one that came out. After replacing this and the other two parts everything worked perfectly, and the fridge is now off more than its on which is opposite of before. This timer triggers the defrost cycle every 16 hours, for 35 minutes per cycle. The compressor and fans are off during that time, and the heater can be seen glowing in the freezer compartment. It turns off before the 35 minutes are up as it's controlled by a thermostat that snaps on the coil in the freezer. Anyway, good product works as designed...