Refrigerator is a big, old top-freezer Kenmore. Model number 363 898 4480 does not get a hit on the search here -- too bad for me! But patience and perseverance are paying off.
I have the classic failed-defrost system symptoms: Cold freezer, warm refrigerator. Exposing the evaporator showed very substantial frost/ice. There could have been more, and it could have been more dense, but the whole things was pretty much covered and obstructed.
I thawed it. I wish I had tested the defrost-ending thermostat first! Oh, well... I had to get the frost/ice out to get to one of the connectors on the heating coil -- it was obscured by a heavy blanket of hard frost.
To my surprise, the heating coil is good. The thermostat is hardwired -- no quick-disconnects or wire nuts. So far, I choose not to cut the wires to test it.
It took forever to find the timer. I read that some Kenmores have the timer in the icemaker. I couldn't find it anywhere else, and one of the thermostat leads goes to the icemaker, so I took the icemaker apart. No joy. Apparently the shared lead was just a neutral. I finally took the cover off of the 'control panel' in the back of the reefer, and there was the timer. There is a plugged hole in the face of that control panel. I always wondered about it, thought it weird. Now I know: pop out the plug and there's the timer shaft!
Having found the timer, I was able to confirm that the contacts that enable/disable the compressor work. I was not able to test the heater, because the thermostat was too warm. I decided to run the compressor for a while to chill the thermostat and see if the heater would heat. My thinking was that if I got no heat, then I'd cut the leads on the thermostat, hotwire it, and see if I got heat.
Lucky for me, I didn't let it get too cold. I ran the compressor for a while, then triggered the timer and waited. I opened the freezer and thought, "Gee, something smells hot." Yet the heater did not seem warm. But when I picked up the heater off the bottom of the freezer, there were melted spots in the plastic the length of the heater! Right, I hadn't actually re-installed the heater, just set it in the bottom of the freezer. One of two things must have happened: either I had not gotten the coil very cold, and so the thermostat opened quite soon, or the thermostat is defective, and opened prematurely. Either way, it was my good luck that I did not have a China Syndrome.
So where do I go from here? I see three probable culprits. The first is that the thermostat could be bad, opening at too low a temperature. My experience of snap-disc thermostats is not exhaustive, but I've never seen one fail that way in other applications. The second is that the timer is not running. I plan to test for this by supporting the heater on something that can take the heat, turning the timer until the compressor shuts off, and then waiting to see if the heater ever turns off. Too bad I don't know how long it's supposed to run! I'll give it 20-30 minutes, and I'll also try to observe the timer shaft for signs of rotation. The last option is that having my sister and her 8-year-old daughter with us for two days (which involved the refrigerator door being open a lot) overwhelmed the defrost cycle, and that all will be well now that I've thoroughly defrosted it.
If anybody is out there who knows, please answer any of my questions:
- is my logic logical?
- how long should I expect the timer to enable the heater?
- how often does this machine defrost?
- should I expect to be able to see the timer shaft turn?
- will I burn up the heater if I let it get good and hot, by running it for the full term of the defrost timer?
***Additional data a few hours later:
It appears that the timer shaft is turning. I wonder if the door might have been left ajar. If the evaporator is SERIOUSLY iced up, will it clear in one cycle? It's been really humid. If the door was left cracked, could it have loaded up too badly to correct itself in one or two days?
Thanks and best regards in advance,
Paul in East Troy
