Hi All... a couple of problems with my furnace, which is a about 18 years old.
1) Furnace gets call to heat and ignitor lights up (recently replaced) and burner with the ignitor starts, but the other two burners do not fire. The other burners are outputting gas (can smell from outside exaust vent) but don't know why these burners are not lighting. Have cleaned burners and heat limit sensors. Don't know what else to check.
2) Playing around with the thermostat and furnace, now the furnace blower just stays on (no gas, not heating). Not sure how to get fan to reset and quit blowing. Have tried turning off power, changing thermostat settings, but still just runs all the time.
you need to pull the burners and clean the pilot track. be sure to reinstall the outer burners in the same location as they started.
the fan problem sounds like a board problem but check to be sure the g wire is not shorted to r
Got frustrated and called a tech. Problem was as you suggested, that the crossover tubes on the burners were clogged and not allowing the flame to reach the other burners. After they were cleaned, it worked just fine.
For the second problem, it was just that the flame limit sensor was tripped and that's why the furnace kept blower cold air even though there was a call for heat. I didn't realize that the little stub on the flame sensor was an actual switch.