Hello experts,

I have a Lennox Signature series furnace which is about 9 years old. Since last window, it make a very loud noise when it start. The noise sounds like a power generator making humming sound.

I would to have some idea where to look at before calling technician.

Thank you.

My guess is the blower motor is going bad. It is possible finding an place to add oil and adding a little of a light machine oil might give it several more years.

Thanks Labman, I will put couple drops oil. Hope that could eliminate the noise.

For give my typo from my original post, I meant last winter, not window. :)