If the flame sensor is not grounded good, the amber light will not come on "ever" also if this unit in an early model 1993-1994 you may just need to install the remote sensor kit. Your new ground will run straight to the board, to the molex plug, the directions that come with the kit are simple and to the point. My guess is since you already have the flame sensor it's been updated, but if the ground is not making a good connection at the molex plug on the board, it will not work, even with a new board, it has to make a good connection at the plug. Until you see the amber light, when its senses flame the thing will always shut down. It could be the board, but everyone I have ever worked on I just had to relocate the ground to the molex plug with the new sensor kit, and it fixed it. If everything else works on it, and it goes through the proper sequence, my bet is it's not the board, you have a ground issue.
Originally Posted by Cosmicmuffin
“Experience is a hard teacher because she gives the test first, the lesson afterwards". -Vernon Law-
"Skilled Labor Isn't Cheap, Cheap Labor Isn't Skilled" - Unknown