How to Troubleshoot & Replace Frigidaire AP6799886 / 5304518034 Defrost Timer

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. 

Replaced defroster heater. 

Defrost timer. now fan works and cold to freeze like it should. 

Replacing the defrost thermostat and defrost timer thanks for getting to me the right parts they all fit well and the freezer is back to woork Roly Chorens 

The 12hr. timer was installed. 

Replaced both Defrost Thermostat and Defrost Timer. 

I replaced the timer and the defrost thermostat, it took about 30 minutes, just got thru so I'm waiting to see how it works before I start filling it back up again, My husband is at work so I did my self. 

I replaced the defrost cycle timer and the defrost thermostat. 

My son owns an HVAC business and is one of those people who can fix anything. He came to our house to replace the door gasket and noticed that the defrost timer wasn't cycling. When he left we had a new door gasket in place and a defrost timer ordered and being shipped. The repair was simple enough so when the part arrived I went and got it off a neighbor's porch ( thanks to FedEx) and swapped the part. I made sure the dial on the timer was moving after a couple of hours then slid the freezer back into place and we were back to normal. 

Replaced the defrost timer. They are the most likely cause of a Refrigerator or Freezer not defrosting. Long time Mechanical / HVAC and Appliance Contractor. And, although I am a PRO - any homeowner with a little ambition can do this. It's an easy fix.