I have a GE side by side with a defrost issue. It began with food on the fresh side freezing a little and food on the freezer side thawing a little. Once I investigated and removed the back panel in the freezer, I realized the evap coils were frozen. From there, I tested a few things.
The Defrost Heater showed continuity, but the glass looked blackish, so I purchased a replacement and installed. I also tested the Thermostat from the main board and it showed ok, but I replaced anyway. The Evap Thermistor tested at a very low Ohm reading so I replaced that last night.
I’ve seen the defrost heater come on twice since I’ve been investigating. Once before I installed anything, and another time last night - 30 minutes after I installed the Evap Thermistor. After that, I haven’t seen it on and I just recently took this photo of the coils.
That is definitely not defrosting itself properly.
When you saw the defrost element come on did it glow nicely? And stay on for a while? 20-30 minutes probably. It should stay on until the thermostat stops it or the thermistor tells the board that it is warm enough. I’m sorry I don’t recall the temp at which they should exit defrost.
If you have definitely seen that heater glow for a substantial amount of time then your problem is likely the board, unless the defrost thermostat is stopping defrost too early.
I’d have to track down a tech sheet to see if there’s anyway to force them into defrost, otherwise it’s up to you to listen for it.
The fan is an easy test, although I wouldn’t think it could cause this. In general it’ll run with the compressor. There may be a few minute delay at compressor start after defrost. You’ll probably need to hold the door switch in or it won’t run the fan, unless the board has it in emergency cool. GE DC fan motors have had some issues. If it’s surging or constantly changing speeds that’s bad.