Going through my pre-season checks. Heil gas furnace, central heat/AC. Sounds fine when flame is burning but when it goes into shut down, combustion motor running to expel fumes, it sounds like a helicopter. Must be some kind of vibration. Furnace is hard to access so I wanted to get some idea of what to look for before I squeeze in there and start taking things apart. First thought was the combustion motor but then why would it not make the noise all the time and not just on shut down? Have run blower motor in AC and summer fan mode and no issues with it.
Thanks for any input.
Thanks for any input.