makolber wrote, on Mon, 22 Dec 2014 10:24:18 -0800:

I suggest you read my previous post that explains how the flame sensor
circuit works.
You can lead a horse to water......
Mark

Hi Mark,
I had read your suggestion and followed it as much as possible.

There is a flame sensor, and a hot igniter, which are located he
https://c1.staticflickr.com/9/8651/1...7fe7ca9f_c.jpg

I don't know yet how to physically 'test' them, but they do not appear
to be damaged. There is absolutely no water, and the ground appears
good but I need to run more tests on ground to be doubly sure.

The good news is that, after wiggling everything and opening all the
vents, and replacing the batteries, I called for heat just now:
https://c4.staticflickr.com/8/7553/1...1d83ee2a_b.jpg

First the first time all winter, the igniter lit after the blower
motor ran for a minute or so!
https://c4.staticflickr.com/8/7566/1...a8d7692c_c.jpg

Then, for the first time, the flame and igniter went on:
https://c4.staticflickr.com/8/7554/1...38cbbba7_c.jpg

Then, just the flame went on, for about 10 seconds or so:
https://c4.staticflickr.com/8/7550/1...b9901d66_c.jpg

This happened three times, in quick succession, and then the furnace
went back to the blinking.

I will post the blinking video separately, as it seems to be
blinking a different code now.