A couple months ago, I noticed the refrigerator section of our ZICS36NABRH was warmer than usual. A check of the freezer section showed the evaporator coil completely iced up. I needed an immediate fix and removed the back panel and defrosted carefully with a heat gun without further action or diagnosis.
A few weeks later the problem reoccurred. This time I manually advanced the defrost timer and successfully defrosted the unit to completion. I figured that meant the defrost heater and defrost thermostat were good. That was the extent of my diagnostics. I replaced the defrost timer.
Now the problem has reoccurred. I manually advanced the defrost timer, and again the unit defrosted. This time I put a mark on the timer to see if it is moving (I assume this is a simple mechanical switch that goes around in a circle). No movement was noted and the defrost cycle did not end (the compressor did not come back on) after 45 minutes. I do hear what sounds like a timer clicking.
I have a letter from GE "welcoming" the original owner to the "GE family" dated 2002 so I assume this unit was built in 2002 or earlier.
I checked the wiring harnesses in the upper section for proper physical connection. FWIW, this problem may have started when I vacuumed the condenser coil and upper section. I was careful when doing this but may have bumped something.
Any ideas greatly appreciated!