I did a bit of investigation. The unit had been disconnected from power since Friday. Connected it, the vroom-vroom-vroom sound immediately began. Traced it to the circulation fan in the fresh food section, not the compressor. Removed the shelves and the air diffuser on the back wall, disconnected the harness and it stopped, resumed upon reconnection.
The control panel normally illuminates when the FF door is opened (or is it lit continuously? I've never checked that) to show the current temps and function settings. It's now blank until any button is pressed, at which it beeps and
(a) FZ temp says -48°F
(b) FF says -38°F
(c) ExpressThaw indicators for 0.5 Lbs and 3 Lbs illuminate and the display says 4 Hr
(d) then it all goes blank after half a second
(e) the buttons don't beep if pressed again immediately
(f) it beeps if pressed after a few seconds wait but nothing illuminates
(g) the sequence repeats from (a) when pressing a button after a bit longer wait
Cubed and Door Alarm (usual selections), and Reset Water Filter (I haven't replaced/reset the filter in a long time) on the dispenser panel are normally lit continuously. Now they're blinking on a 2 or 3 second repetition (all lit or off at the same time). The dispenser panel buttons don't respond when pressed to change the settings.
The compressor was warm when I discovered the problem on Friday morning. It's cold now after power being disconnected over the weekend. No evidence that it's trying to start on power now.
I haven't had opportunity to do further diagnostics, amperage, voltage, and windings tests, some other ongoing concerns are in more urgent need of attention. The refrigerator is next to the range and there's a freestanding but *heavy* island-cabinet in front of them which limits how far it can be pulled forward unless everything emptied out of the island-cabinet for moving it. There's not much working room, just enough gap to squeeze through behind it.
Would a bad inverter board cause those symptoms? Or is the motherboard more likely?
The plugs not connected to the board are presumably due to the substitution when it was changed in 2010 ... I've slept a couple times since then for recalling the details at the time.
