First I took the technical data sheet off the back of the unit, it was in a brown envelop taped and tucked into the lower equipment cover. Then I compared information from Appliance Parts Pros to the data sheet, matched up the probable culprit parts, and ordered defrost thermostat and defrost control. They arrived promptly..
Unplug the unit from the wall. The defrost control is located in the same space as the light, two screws and the small panel drops down, a tip is to use a short #2 Phillips and let the panel drop down on a shelf. From there detach the panel wiring harness, five pins, set the panel on a bench, change out the module, and reverse the process. Another tip, this is probably not a place for a power driver.. Then, open the freezer cabinet, the shiny screws give access to the coils, the thermostat is clipped to the line shown in your technical data. Un-clip it, cut the wires at the thermostat, clip the new one on, use wire nuts or crimp connectors to splice into the harness, color to color, reverse the process.
That is the part replacement process. It takes about forty five minutes. Then, see if the parts work, and they will.
What comes next is about an hour and one half. Cleaning the condenser coils. My technical data sheet shows a set of coils under the fresh food cabinet formed to curve up six inches to vertical. Which makes a fan pulled shelf for dirt. If you want to try to clean this, try to take the unit outside. It is not possible to clean this set of coils by vacuuming or brushing it from the bottom or back. It need to be blown out. And it will make a terrible mess. If you use one vacuum to blow, use another to catch the stuff.