My relatively new Kenmore Elite chest freezer, model 253.17802411, thinks that the door is ajar even though it's closed. Seemed like the door switch was OK because the light went on & off, so I replaced the control board. But it was the door switch after all. Cleaning the door switch contacts with DeOxit fixed the problem. [NO, NOT QUITE. SEE PART 2 FOR THE REAL FIX.]

So, here's a video that shows replacing the freezer control board. I now have a spare if anybody wants to buy it. It's Electrolux/Frigidaire #5304500220. I got mine from Amazon.

Not too hard to replace. Would have been easier if my hands were smaller!

Note that this procedure should also apply to similar Frigidaire and Electrolux freezer models. Also, the Kenmore 253.17802410 model is similar.