Defrost Thermostat - How to Test and How they Work 

This makes a lot more sense than the video. If it didn't close until temp cooled down to 20°, then how could the ice water test ever work when icewater is 32°?

Excellent. That’s how it works not like the guy says in the video, that’s misinformation there

Derek Kano Awesome!

Bill, after a week it started frosting up again. I also forced a defrost cycle after this and I hear two quick relay clicks in succession? Looks like I still need to change the adaptive defrost control board. Do you think it damaged the defrost thermostat as well?

Derek Kano Changed the ADT Control Board, seems to have resolved the issue. Looks like two parts were bad.

Thanks!

rtmoynahan2 Thanks!

Cup of ice water will only get down to 32 degrees. Maybe less if you add salt. Depending on switch design limits.. a freezer stat will be set to 10 degrees or much less.

You're Welcome! Thanks for the great comment and Thanks for Watching!

Thanks!

Yes you will run into problems!!! The heater element will get red hot, your fridge will warm up way too much. It could melt the plastic near the evaporator coil and start a fire. The defrost timer typically spends 20 minutes in defrost. It typically doesn't take near that long for defrost. That's the purpose of the defrost thermostat (aka defrost termination thermostat, or limit thermostat)

Moustafa Najjarine hello, I’m going to attempt to answer your question with a “possible” answer from a TOTAL LAYWOMAN’S perspective as, I had the same issue with my GE top freezer TBX14SABNLWW refrigerator and because Bill is not able to answer questions since I hear he is deceased (RIP Bill). I started having the symptoms of the freezer over freezing with ice coming into the back wall of the cooling compartment, then then I fixed the slight gap in the freezer door gasket, thawed it for 1 hot day, where my refrigerator started working great again - for 2 days. Then, the cooler compartment went to 65-70 degrees. Because a number of videos say that it’s often the defrost timer and that was cheap and easy to replace, I just did that this past weekend. It’s almost as easy as plugging in a lamp. I’ve also replaced my cooler door gasket, ensuring that it is properly formed (with a hair dryer) for a perfect seal, especially during the heatwave we’re having. So, it’s been 2 days. Things seem to be working great. Better than great. Now I’m worried again. Why? Because I have my refrigerator turned down to “2” (1-9 dial). How it’s working so efficiently in 95 degree weather is what’s worrying me. Makes me wonder if the defrost heater is coming on at all, but before buying food again, I’m waiting and seeing for a few days. Because, if it’s this cold, with a setting of “2” on such a hot day, what happens when the weather starts to cool? OK so, where am I going with this? I call it the possible “boomerang effect”. Once you’ve melted the ice on the evaporator, which had been blocking cold air to the cooler section, unless other components of the defrost system aren’t working properly, it might seem as if it works better than a brand new fridge, unless and until ice builds again. If that happens, it’s back to ice cold freezer and warm fridge. For me, if my fridge starts to warm during the next few days, I’m going to assume that, although it was an easy and cheap replacement, it wasn’t my defrost timer. It might then be the defrost thermostat or a dead defrost heater. Again, I’m not at all an expert. My next step is to see what it does when the weather gets cooler. Because one cannot turn it much further down from “2” come winter.

Test it when it's cold inside the freezer

RoyFavre1 Replace the compressor relays, make sure the fan by the compressor is running, clean the coils underneath. Thanks for Watching!