Fridge was freezing at bottom, not cold enough at top. Cold air was not coming in from freezer through damper at top of the fridge. I checked the damper and it was opening OK. Next I checked the evap. fan in the freezer and it was running OK. The evap. coils were frozen over (mostly at the top). I defrosted it and checked the defrost heater (even though I noticed that it had come on while I was inspecting things) and it had continuity (~22 ohms). I then checked the defrost thermostat which seemed to have continuity whether it was cold or warm. Could this be the problem (causing the defrost time to be too short)?

I read that on some GE refrigerators like this that the defrost thermostat is only a failsafe and that the cycle is actually controlled by the main board using the thermistor on the evap. coil. Is this true for this fridge? I didn't have time to test the thermistor and just put things back together. It's working fine now, but will likely return to it's former state soon.

I also read that partitial evap. coil freezing is a sign of a refrigeration system problem. Any advice on this?

I guess I'll check the thermistor when I get a chance. If that's good, next would be the main board if it is a defrost problem.

Before I took things apart, I was just monitoring what the fridge was doing. The evap. fan seemed to be running all the time, but then I noticed that it shut off. I looked in the freezer and the frost that had built up on the back panel was melting at the bottom and the panel felt warm. I assumed this was the defrost cycle starting.

Maybe I just didn't let the overtemp. thermostat get hot enough to open when I tested it. I hit it for a little while with the hair dryer I was using to defrost the coils and it tested closed. Then I put it in a cup of hot-ish water for a few minutes and it still tested closed. I was assumning that it would open at a much lower temp. than 140.

I haven't checked the evap. coils since I put it all back together. I'll take a look tonight if I can and post a picture if anything interesting is happening.

Here's a picture I took last night of the evap. coils. It had actually been 4 days since I did the checking/testing/defrosting on 1/20. Looks like a fairly even coating of frost, slightly more concentrated at the bottom.

So after about 2 and a half weeks it was back to acting like it was before. Here's a picture of the evap. coils. It's fairly clear at the bottom with most of the thick ice in the middle. It looks like it has been defrosting somewhat in that there are frozen "drips" on the ice and there was some water frozen in the tray underneath below the drain hole.

Could it be just not turning on the defrost heater for a long enough time? I defrosted it and for now it's working. Maybe I'll check the thermistors this weekend.

Thanks for the advice. I ordered a thermistor yesterday. I'll replace it and let you know what happens.