There are lots of advice for homeowners to maintain the heating system. If the furnace is running, but you can’t find any temperature difference in the room, then you need to check the ducts and the blower of the furnace. In the heating system, people never bother to check ducts even in the regular maintenance.
http://furnace-air-conditioning-repair.blogspot.in/2015/06/how-to-clean-your-furnace.html