It is similar to many posts before. Fridge is warm. Freezer evaporator coil has iced up. I opened the back panel, seeing the heating is not working.
Strange thing is after opening the freezer door, complete defrost the coil manually, the freezing/defrost cycle is working again. The heater is clealy working.
The coil was frozen many times before and I can restart it by manually defrost It. What can be the problem? Defrost thermostat? temperature sensors? Control board?
How to test the sensors? Do I need to cut/open one wire to get an accurate reading? I measured the resistance by inseting needles into the wires. The Defrost thermostat has ~0 Ohm resistance.
Remove the three pin, gray power connector from the motherboard and stick a wire jumper between the connector pins as labeled on the motherboard, line and def. Assuming the freezer is cold, once the fridg is plugged in, it should defrost. If not, you have a bad defrost thermostat. If defrost, I would still replace the defrost thermostat as it appears to be intermittent and also replace the motherboard.
It is also possible the evaporator thermister is shorted, just check if you have a ohmeter, should be 16.6 kohm at 32 dgrees.
Thanks for the help. Probe the defr line (vs. fridge frame), it’s 0V AC. Other 2 lines (COMP, LINE), both has 120V AC. Instead of jump the defr line, I just wait for fridge defrost to kick on (then check the volt).
I’d assume it will work (intermitten). To save few $, do I really need to replace the board? Question is which part (thermostat or board) is the problem. I disconnect the J7 (looks like it is connected to the thermostat). Measure the thermostat wires at cold/warm temp, both are at ~0hms. Is it right?
The only way to test the motherboard is to do the test I descibed above.
The evaporator thermistor is a long,white item clipped to the top of the evaporator coils.
Because it’s intermitten, I left the freezer runs for a week to observe. Interesting to see the freeze and defrost cycles continue.
However, I’m seeing the ice build up (even with defrost cycles). Now, about top 1/2 of the evaporator coil is thick of ice, and bottom 1/2 is still ok.
Can the problem be the "weaken heater"? We have the fridge for about 5 years.
There are 2 temperature sensors in this freezer, item #241 and #242. Do they both need to be replaced? I’d assume they can be called "evaporator thermistor". Thanks.