How to Troubleshoot & Replace Whirlpool AP4246797 / R0131577 Refrigerator Defrost Timer

I replaced the defrost timer kit first. This was easy on my refrigerator, (Kitchen-Aid bottom freezer refrigerator, KBRS22KGBL00 ). AppliancePartsPros.com has a good & easy to follow video on how to replace this component. I replaced the defrost thermostat next, which was bulged from over heating when it failed. Make sure you have all the supplies and tools you need before starting this repair! Also make sure the new defrost unit is good electrically before installing. The video for this was on a side-by-side refrigerator-freezer and not my model. After defrosting the freezer for at least 24 hours and making sure there was no ice built up on the back panel of the freezer I removed the screws except the ones closest to the ice maker. Not sure if this is the way a professional repair would be done but I gently formed NOT FOLDED the back panel so it had a gentle radius bend and moved it towards the ice maker that my unit has. Using duct tape, I held the panel out of the area I needed to work on. I made a note of which wire colors the old thermostat had and the colors of the wires they connected to. There are plastic connectors on the new thermostat and the refrigerator but they don't fit each other. I cut the connectors off both the new defrost thermostat and the old one leaving as long a wire as possible on both so I could connect wire to wire using solder splices. Make sure you have a variety of splice sizes since one of the connecting wires is bigger because of its insulation. After connecting the wires and completing the installation of the solder splices, I attached the defrost thermostat to the coolant pipe as shown in the video. The video has good information and is still worth watching. If you want, take a photo of the repair before you work on it so you have a reference when you put it back together. Test the repair by plugging the refrigerator in and manually turning the defrost timer until it turns the cooling system and fan off. Wait for a few minutes and carefully feel if you can feel heat from the evaporator heat element. It should be HOT so be careful. If it is hot you can cable tie the wires you worked on out of the way and remove the duct tape from the back panel (make sure the back panel goes into the little trough/gutter of the panel below it so moisture go where it should ). Replace the screws and you are done unless you do what I did and bump the container of panel screws and then not be able to find them all, oh well found some other screws in the kitchen junk drawer. I have to turn the temperature to six out of seven on the temp control but it works and holds the correct temperature now with no frost build up. My guess is this refrigerator is close to 15 to 20 years old. A repairman quoted $300.00 for the repair. 

After doing some research, I guessed it was either a faulty defrost timer, defrost thermostat, defrost heater, or some combination of those. Using part location diagrams for my Amana BC120TW I started by looking for the evaporator coils since they obviously weren't producing enough cold. Upon removing the evaporator coil cover, I found the evaporator coils frozen into 1 solid block of ice. Using a heat gun, I carefully defrosted the coils so I could access the defrost thermostat and heater for testing. The thermostat was obviously in need of replacement since it appeared water had frozen inside of it and caused it to pop open. The heater also did not pass a continuity test making me think it was also broken. However a little more research on defrost heaters told me not all heaters will pass a continuity test, but will have an ohm reading. The old heater tested out at 29.8 ohms while the new one from AppliancePartsPros tested at 30.2 ohms. Since they were essentially the same, I knew the heater was still good. The only thing left was the defrost timer which I replaced since it was the original electro-mechanical part containing a motor and timer mechanism, and also the cheapest part to replace. I don't know whether the defrost thermostat went bad preventing the defrost heater from working, or whether the defrost timer stopped working again resulting in the defrost heater from working and freezing the thermostat. In any event, I have a new defrost timer and thermostat and a refrigerator that is back working as it has for the past 25 yrs. 

After running some tests I determined that the problem was a bad defrost timer. The timer would occasionally fail to trigger the compressor to restart at the end of the defrost cycle. Since I had the unit taken apart, I replaced the termination t-stat and the compressor start relay at the same time. Parts came quick 1.5 days, job completed and the unit is up and running. 

Ordered a new defroster timer on Monday morning. Received the new timer from Appliance Parts Pros the following day. They know how to treat customers. 

Removed bottom half of covers in back of freezer compartment. Coils frozen on top half and around evap fan. Defrost thermostat bulged and probably the problem. Melted ice with hair dryer. Had already ordered defrost timer and thermostat from A.P.P. regular shipping, received in less than two days. Replaced both, everything is working well. 

Tested start relay and fan with multimeter both passed. The condenser would start only if the thermostat was on the highest setting and the refrigerator would cool for a while, stop and not restart unless I adjusted the defrost timer. Decided to replace the thermostat, defrost timer and defrost thermostat. The refrigerator is working as expected. FYI on a Kenmore 59669142992 the defrost timer is located under the freezer in the front right. 

Research showed likely cause, ordered new $20 defrost timer on Sunday, it arrived Tues AM. A 10 min repair saved us!! 

Replace the defrost timer kit..........it works like a charm both sides are freezer ready had to turn down was freezing things on both sides... 

Replaced timer, it worked great. Frig back up and running. Shipping was extremely fast. 

It was determined defrost timer was defective, ordered one, replacement worked wonderfully. The timer removal held by two screws hold timer to freezer, once removed a 4 terminal connector attaches to side of timer. Pulled connector from timer then connected new timer and connector, re-attached timer to freezer. operation took 15 minutes.