I am trying to determine if the evaporator coil defrost cycle is controlled by the motherboard or if there is a separate defrost timer? I have checked the heater, defrost thermostat and evap fan. All are working OK.
For defrost failure, you may need a new motherboard AP4436216
Unplug fridg, remove the motherboard cover and remove the 3 pin power connector. Place a wire jumper across the mating connector pins that are labeled line and def. on the motherboard. Plug in fridg. if you get defrost action, you have a bad motherboard, assuming the freezer temperature was below 20 degrees.