Have HVAC Questions? Ask an HVAC Expert for Answers
My name is Billy.
I am afraid it is bad news. The flame is blowing back because you have a bad heat exchanger. This is like a car having a blown motor....it is the worst thing that can happen. The flame is blowing back because there is a hole or crack in the exchanger.
When the main blower kicks on it blows air through this crack and washes flame backwards.
I am very sorry for this news, but I wanted to be up front and not waste your time. You will need to call for service and will end up replacing exchanger ($900+) or replacing furnace.
I understand..many here wont take bad news questions as they dont want a bad rating....but I believe in being upfront regardless..
I apologize for the news and wish you the best.