I was surprised (in a not so good way) yesterday afternoon when I noticed our furnace fan wouldn't come on.
Normally I would turn the central fan on and most of the time the resultant air circulation is such that air conditioning isn't needed. But something was wrong.
I called D and we decided to contact the heating contractors who installed our furnace 3 years ago. We have a high efficiency Lennox furnace with a 10 yr warranty.
Good thing I called because I found out that that particular model and year has known issues with its control board.
They were able to send someone the same day as they were in between seasons and it literally took only 20 min to diagnose and replace and voila, we have a working unit again all covered under warranty.
I was nervous not knowing the extent of the problem and how much it was going to cost. Same kind of nervousness I get at the auto mechanics.