Hi, my name is Mike and I have been in the home improvement and repair field for 20 years. I will be very glad to help you today. Is there any ice build up or water on the inside or ice on the back? Also the evaporator is on the inside on the back, if you remove the panel do you see ice on it?
Does the temperature fluctuate or is the temperature lower than the setting?
How are you testing the temperature? Is the thermostat at a low setting?
To accurately measure the operating temperature of the fridge you can place a thermometer in a glass of water and place it in the middle shelf of the fresh food compartment.
To get an accurate reading it may take a while with the door closed.
The sequence is the power on ,then liquid solenoid then low pressure switch then compressor starts freezing, then fans come on then timer activates defrost mode, liquid solenoid closes defrost for about 30 minutes or so then compressor back on. If there is ice on the evaporator that is a good sign that the timer is not working properly.
That particular model I have not worked on. Usually if the board is not working then you will have no function as the board does not operate the thermostat.
I do not think either but if you are suspect of a capacitor they are very easy to assess. Unplug the power. If you look on the back of the unit there will be a square metal panel. Remove the screws and remove the panel. Remove the plastic cover. You will see battery looking things on the board and those are the capacitors. If the tops are not perfectly flat or bulging out the sides that is a blown capacitor. If you can solder a bit they are really easy to replace also.
If one does need replacing it has to be exact. The numbers are on the cap itself. On the side. Capacitors have gotten bad in the last decade for sure. Since the technology was stolen from China now most are made in Taiwan. Could be the capacitor on the board. That is always a possibility but I still think the timer. You can assess either very easily if you are up for it. You will have to do a little exploratory surgery to be sure. Of course if you have a lot of items in the fridge that can also be the simple issue. Be sure no items are blocking the damper vent. Could simply be that.
So if you check 1. Items not blocking damper vent. 2. Capacitors on control board not bulging. 3. Evaporator does not have ice build up on it. That will give us some great information to proceed with.
I have to step out for a few hours. Let me know what you find and we can go from there. Ok?
Were you able to check out those items?