MajorApp, as a technician, I assume you have meter. (Actually, I am assuming you are a technician.)
This is the Wide by Side refrigerator....
If you want to see if the defrost heater and terminator are OK, set the meter to read OHMs, unplug the single, simple harness to the heater/terminator loop in the freezer and check continuity thru it. That will tell you:
a) The heater or terminator is either good or bad
b) If heater is good, the ADC board is bad.
If you want to initiate a forced defrost with this kind of adaptive defrost control, you have to take the control panel apart to get down to the board, then short across the 2 test terminals on the board with your screwdriver to start the defrost cycle. You may unplug the unit to stop the cycle and resume cooling.
BTW, the heater does NOT come on whether in manual defrost or otherwise if the terminator is open.