Dear KAG: 20201201 Open Thread

What is she referring to?

Sorry — got distracted last night, then fell asleep.

;Anyway, I had gotten through the freezer cooling. Cold coils at the top, cold air settles, warm air rises, hits coils at top. The way the fresh side gets cooled is that a little door (“damper”) at the top of the fresh food section is opened, and a fan on the other side (in the freezer) blows cold air through it. At the bottom of the fresh food section is another little door, which also has to be opened — otherwise the fan can only blow against the air pressure in the fresh side and not actually move any air. This is controlled by a custom microcontroller that handles all lights, displays, etc. That’s it — four components.

Two of these had previously been replaced chasing the same issue — the computer and the upper damper — by a supposedly reputable and knowledgeable appliance repair place. When asked to actually fix the problem, however, they demurred and said we should consider buying a new unit. The actual answer, of course, is that the bottom damper is sticking — which makes sense, because any wet crud that gets spilled at the back of the fresh compartment will trickle down on top of it. I’m about 95% certain of this.

Now, the last time this glitch occurred, back in September, I took all the “user” stuff out of the fridge and cleaned it. I had intended to actually look at the bottom damper and be sure that I was ready to replace it before I ordered one — but when I got there, there was this box siliconed to the bottom of the fresh section. Logically, it contained the bottom damper, but also a bunch of stuff relating to the “climate control drawer”. That latter is a special drawer that you can use for chilling wine or other things. The “Express Chill” button has 3 options: 15 minutes, 30 minutes, or 45 minutes. The drawer itself has a hole in the back that seats some weatherstripping on this box. I realized that the way “Express Chill” had to work was by using its own little door into the bottom of the freezer, and using its own fan to bring over some cold air and using its own little door to blow warm air back into the freezer.

So the symptoms caused by the failed lower damper are that the freezer gets colder and colder and the fresh compartment warms up a bit (nominally, they are at 0 degrees and 37 degrees). The reason for this is that the computer successfully opens the top damper and turns on the fan, then preemptively runs the freezer cooling for the temperature rise it expects to have from having a bunch of fresh compartment air released into the bottom of the freezer. Since that warmer air never gets into the freezer, it just keeps doubling down on stupid.

The “bobble” that I figured out by taking apart so much of the fridge, is I can take the drawer of the “Climate Change Drawer” out of the fridge, and use “Express Chill” to open the little independent CCD damper.

As an example, I checked the temps at 11:14 pm on Oct 12 and got -10/42. I ran Express Chill for 45 minutes and got to -8/40 by 12:40 am on October 13, whereupon I ran Express Chill again. At 2:03 am, the temps were -1/38.

I’ve done this pretty much every day since mid-September, sometimes doing little change-ups to see what difference they could make. On November 28, however, the main fan started making an unpleasant noise — this generally happens when there is an ice buildup on the coils. There is a way to switch the fridge into manual mode and force a defrost — I’ve even done it before — but I forgot the way to do it. I informed the Fiancee that she should get some of the more sensitive items out of the unit and went off to find the manual defrost method online, and came back to find that she’d had both compartments open for a substantial period of time — which meant that there was condensation throughout the unit. I’d have to take the unit down until the ice thawed on the coils and ran down to get mopped-up and the condensation evaporated.

I then rebooted the fridge and monitored its cooling hourly from 11:30 am on November 29. It’s been behaving as expected, except for one little detail — the PID programming doesn’t like the unit being empty, so the temp hasn’t been as stable as usual. I checked this by adding a bunch of beer which did help. I waited until sufficient hours had passed that it did its own defrost cycle (six to fourteen [?]), and it has been released back into general use.