After some internet research I determined it was either the defrost timer or temperature controller. I ordered both parts for the repair. I started off by replacing the defrost timer since it was the easiest. Unfortunately it was not the problem. I then replaced the temperature controller and and it solved the problem. The only tricky part of the repair was bending the sensor bulb to fit in the location where the original one was located. Also, I did not have to take the entire access panel off to get access to the temperature controller as shown in several videos. I loosened all the screws and just pulled back the top portion. This made it easier to ensure the seal around the access cover stayed in the proper position.