There are basically 3 possible 120 volt failure modes
ONE (And this is a 2 parter) No 120 volts to the Fridge outlet or a bad connection on the terminal board or elsewhere
Two (in power flow sequence) Bad control board
Three: Bad heat element
Now on my dometic there was a design fault...
The terminal board which distributes 120 volt both to the control board and hence to the heater and the ice maker is bottom center in the outside compartment
There is a drain tube that drains the water that drips off the fins when the frost melts that hangs directly above this board... You are SUPPOSED to extend that tube out through one of the holes in the outside vent cover. but when I got mine.. That was not done. So the water dripped, dripped, Dripped right on the 120 volt distribution board (Oh it has a fuse) I moved it out..
Well when I got the Recall I mentioned to my service consultant and the technician returning my keys said "I always put it out" (Liar he had not).
There are also fuses in the black box bottom left corner I know some of those are 12 volt Do not know if there are 120 volt there.
