On Tuesday, December 23, 2014 9:37:04 AM UTC-5, Danny D. wrote:
Danny D. wrote, on Tue, 23 Dec 2014 13:21:56 +0000:

So, *both* the old and new LED indications point to a suspected lack of
"earth" ground (among other things).


If the ground is affecting the flame sensor, then it't the ground path
from the metal cabinet/frame of the furnace to the control board. That's
where I'd be looking. There must be a ground wire that goes from the control
board to the frame and the frame is also grounded to the incoming AC.