Furnace blowers often fail to work when there is a problem with the power supply, thermostat, filters, vents or the motor of the blower. A homeowner can troubleshoot problems with the vent himself or call a professional to take a look at the unit.
Reasons the power might be out on a furnace include power surges, storms and electrical outages. Checking the fuse box or service panel for the HVAC unit first is the best starting point for malfunctioning surface blowers.
Incorrect thermostat settings can also cause a furnace blower not to work properly. If the thermostat isn't set at least three degrees above the room temperature, the furnace is not likely to turn on. Homeowners who have digital thermostats should check to see that the batteries work.
Closed vents and dirty, clogged filters can lead to problems with a furnace blower. It is also possible that the filter was installed in the wrong direction. Homeowners should check the filters at the cold air return to ensure the arrow on the filter is pointing toward the ductwork.
The door of the furnace blower motor should be closed in order for it to work properly. Other problems with the blower motor that can cause the furnace blower not to work include cracks in the belt and overheating.