Hello,
I have an armstrong air ultra 80 V 45647-001, I'm having an issue with the top motor staring burners igniting and staying lit for roughly a minute then the unit shuts down usually without the bottom blower motor kicking on. I have left the fan on constant to help keep the unit cooled down thinking it was an overheating issue. I changed the thermostat (honeywell)a few days ago and put it on auto and it worked fine until recently (I'm a new homeowner and have only had the house a couple of months and this is a nagging problem). Should I just break down and call the experts? I take pride in fixing things myself however have little HVAC experience. Any help would be greatly appreciated.
Thank You

U might try cleaning the flame senser, use fine steel wool