Goodman Gmp075-3 Burner Intermittant

DMC

I have a Goodman GMP075-3, 80% furnace. The vent circulator comes on, ignitor comes on, burner ignites, then the burner usually only stays on for 5-10 sec. and goes out. The furnace then cycles again igniting the burner. Sometimes (75% of the time) the burner takes 2 or 3 times before it stays lit. But the other times everything works fine the first time. A couple times the furnace went into lockout and flashed the LED 1 flash. I checked the voltage to the gas valve and it is 25V when the gas is burning and the voltage does go away at the same time that the gas shuts off. So I guess the gas valve is good. The vent blower is working and pulls vacuum switch closed. I had a furance guy come out who swapped out the flame sensor and left, but the problem is the same. I called him back out and now he thinks it is the fact that I don't have a chimney liner. Is that possible?? He looked up the chimney and it is clear. I think it is an intermittent control board problem, any guesses???

NickTech

clean the flame sensor