Hey Folks,
Lot of smart and helpful folks out there in SMC land that I tend to trust so...

- Came home yesterday after being away for 3-4 days and found that our fridge was now at room temperature, even though the freezer was cold. (Does weird things to the milk, let me tell you... )

- This is a Kenmore 596.69272 Bottom Freezer (no water or ice maker or any extraneous doodads) And I forget exactly but probably 12+ years old.

- Did some poking around and googling and tracked it down to the fact that something was obstructing the airway that brings cold air from the freezer to the fridge. I could feel that there was no air movement at all out of the air channel in the top/center of the fridge. Another option was that the fan that blows air up from the freezer was busted.

- Took off the bottom back cover and the compressor was running fine, and no fuses there to check. Vacuumed out a ton of dust bunnies and closed it back up.

- Took off the inside back cover of the bottom freezer compartment. The coils/fins there were totally frosted up. The fan was still working, but the return air channel was chock full of frost/snow. (The fan blows air up a duct in the middle of the fridge which exits at the top of the fridge compartment. In the back/bottom/left of the fridge compartment there is a return-air duct which opens into the hidden compartment where the coils are located. There is a duct that guides the return air to the very bottom of that compartment.)

- Totally defrosted everything, closed it back up, and plugged it back in. It was now blowing cold air out of the top channel into the fridge. We left it over night (It was now empty) to get back down to temperature. This morning both the top and bottom compartments are cold. The fridge is about 3-5 degrees Celsius (37-39f) and the freezer is on the cold side at -12-15c (5-10F)

- My brother had a similar issue when his freezer was brand new, and the service tech defrosted his unit and reseated the heater coil and it has been fine since. The tech's comment was that sometimes the drain to the evaporation pan can get plugged by some small particle and then the unit freezes up. This seems a bit unlikely, but of course it would be nice to hope that our unit is fine now.

- I popped off the back cover and the coils/fins are NOT a solid block of ice, which is a good sign, I think.

- Here comes my question to any experienced folks out there. There still is SOME frost on the pipes that run through the fins. Any idea how much is okay? (Some of this is within 1" of the heating coil, which is why I wonder if there should not be any frost.) Any idea how to tell when the unit is cycling into a heating cycle so that I can check if the heating coil warms up? Any other suggestions out there?

Thanks in advance, this is not how I was planning to spend my vacation!
...art