This is a follow up question on my KitchenAid Bottom freezer fridge.
I followed the steps you suggested and tested the defroster thermostat. It was ok. The fridge worked fine a for a few days after I turned the freezer off. It is now frosted up again blocking the cold air flow to the upper fridge. Could it be the defrost heater (same as the evaporator heater?). How does one get access to the defrost heater to test it? Is it from the back of the freezer?
If this is not the problem, what could it be? One of the other thermostats? Thank you again for your suggestions.
A way to test the system would be to put it into a defrost cycle. If you remove the rear wall in the freezer compartment, and access the defrost timer which is under the controls in the refrigerator compartment. Advance the timer until it clicks. Once it clicks allow to sit with the doors closed for 15 minutes. After the 15 minutes check to see if the ice on the coils have started to melt. If so then replace the defrost timer 67001036. If the ice has not started melting then you will want to check the continuity of the defrost thermostat and the defrost heater. The heater can be checked by disconnecting the wires on either side of the unit that attach to the metal air blocks. If the heater does not have continuity then replace the heater 67002493. If the thermostat does not have continuity then replace the thermostat 12001937.