I have a Goodman GMP100-5, age uncertain, maybe 6 years. The burner fired up for 7 seconds or so and turned off. After 3 cycles it went off. The status light blinked once. Since the gas fired OK. I replaced the flame sensor. It still does the same thing after the flame sensor replacement. It is a 80% efficiency, forced draft and pilotless unit. A few days ago, the blower fan did come on a few times on its own, with the thermostat turned off. Is it an indication that the control board or the thermostat may be bad? A couple of months ago, when it was in cooling mode, the condensing unit would turn on for a while but would not keep running. I cleaned the thermostat and it worked OK. Suggestions anyone? Thanks a lot.

If checking the flame sensor connections to the board doesn't help, I am afraid the board is bad. I hate to see you cough up for a new one and it not be the problem.

Thanks labman. I did check the connection. I guess I have to bite the bullet then.