Here is the wiring diagram
ftp://ftp.electrolux-na.com/Pr...F/Anderson/240389604.pdf

You will probably have to remove the cover from the evaporator coils to check that they are heavily iced over which would indicate a defrost problem.

Also check that the freezer fan is running when not in defrost mode.

I believe you can force it into a defrost by pushing the fresh food light switch 5 times within 6 seconds. Same procedure to turn it off. Note the light bulb must be working. Also the defrost thermostat must be frozen so it is closed. It is open when just above freezing. Hold it on a piece of ice or in a glass of ice if you have to.
This will at least tell you that the defrost heater is working and that the defrost thermostat is closed.
It does not tell you that the defrost cycle is running automatically so you may still have an adaptive defrost board problem.

It will run fine for 3 or 4 days, and then it will thaw for 12 to 18 hours before coming back on (during this time the compressor would make a very low humming sound off and on). Then it will start the cycle again. I did notice this last time, some ice on the back of the freezer compartment.
Could the humming just be the condenser fan?
If the compressor is getting power and it is not compressing the gas which the above seems to indicate then you have a problem in this area.
I would first check to make sure the compressor is getting 120 volts.
If yes then it could be the start relay (PTC). Remove it give it a shake if it rattles replace it. I sort of doubt this is the problem as usually the compressor will overheat if it does not start running and you would hear the overload clicking on/off.


Does this mean my defrost heater is out, causing a thaw without the heat from the element which is why it take 12 to 18 hours or is the defrost thermostat faulty?
Not sure. Usually the only way to defrost is manually.

Hopefully someone will jump in who has actually worked on this unit.