We saw that the ice cream in the freezer was soft and the main refrigerator section was not cold enough. Called for repair but soonest appointment was a full week away. So I spent the next few hours online learning how to diagnose and repair refrigerators.
When I opened up the back of freezer compartment to access the evaporator coils, I found ice and frost totally blocking the cold air flow. Turns out the bottom one of the two heater bulbs (quartz heater bulbs) was bad, so both heater bulbs (connected in series) were not working and there was no heat to defrost.
I shut off the fridge with the main temperature control knob and defrosted the coils with a heat gun, catching the water in towels. Now the fridge could work keeping the food cold until I could get the parts. It would eventually freeze up again, but before that, I would change the parts. I closed the rear panel and put back the shelves and food. I turned back on the fridge and then checked the defrost timer in the main food section. I put a mark on the moving shaft and made sure an hour later that it was turning. It was.
For the next few days, it worked great. When the parts came three days later, I first removed the freezer food into a second freezer we have, and I put a big bag of ice into the fridge compartment to keep the food cold. I shut the circuit breaker to the fridge, removed the freezer shelves, and opened the rear panel. The evaporator coils were again frosted up, but not bad enough to stop the airflow. I again defrosted it with the heat gun, catching the water in towels.
I then removed the bad heater parts and replaced them with new ones. The parts came pre-wired including the heat bulbs and the thermostat. They just simply plugged into the wire harness. All it took was a few screws to mount everything. I put back the rear panel of the freezer compartment, but just rested it in place (not screwed in yet), so the coils could have proper airflow. This was for the freezer to get cold, so the thermostat would allow the heater to work, to be tested.
After turning the circuit breaker to the fridge back on, I let the fridge get cold. I then moved the back panel so I could see the coils. Next, I advanced the timer until it clicked... the compressor shut off and the heat bulbs lit up!!
Wow! I fixed it! It will now defrost again! I closed up the panel, put back the shelves, and when it got cold enough, put back the food and removed the big bag of ice. Repair job took time, but it was easy and straightforward! Glad I did it myself!