"There are several reasons that a furnace fan might stop working at one point or another. While many of these do require professional attention, there are probably some things you can check on your own before you go and call in the pros. After all, if you can address the problem on your own, it will at least save you from having to pay a technician to come out.
The first thing to check when your furnace is running but the fan isn’t turning is whether or not the fan is actually switched on. Certain models of furnaces have a separate switch to turn the fan on and off. While there is probably no reason that you would want to turn off the fan by itself, it’s worth taking a look just in case. If that really is the problem, you’ll be up and running and back to dealing with better things in no time.
If that’s not the problem, you might try looking to see if any wires leading to the fan are loose or the fuse is blown. If the fan has no power, of course, it won’t be able to work but the rest of the furnace likely would work just fine as long as it doesn’t run on electricity as well.
Of course, the problem very well may be beyond your power to solve on your own. Don’t despair though. Even though you need to call in a professional, that doesn’t mean that the problem will be expensive to fix. In fact, it may be as simple as replacing your thermostat or the motor for the fan itself.
Just because a fan isn’t working doesn’t mean that you’re going to be paying an arm and a leg to have work done on your furnace. If you can’t easily discover the problem on your own, however, or if you’re not comfortable inspecting this type of equipment at all, you’re generally better off just calling in an expert and letting them do the dirty work for you. Paying for simple furnace fan repairs is definitely preferable to having to pay someone to fix the fan and the stuff you broke yourself while trying to fix the fan on your own."