Every time our furnace turns on, it fills the house with an odor of something overheating. My husband checked the flame and says that it looks normal -- blue. He also changed the filter, which was very dirty. What could be causing this, and what remedies should we try?

Check the heat exchanger it may be to be cleaned. Over time dust , lint and other items become attach to it .

Can we have some more information about what kind of furnace this is and if it have A/C too?