Most newer furnace models are designed for reliability, if worked on well, over a long period, then furnaces are 1 of the most needed and lavish appliances in almost every household! Reasons for your furnace not working can be complicated or straightforward.
You are better off leaving the complicated problems such as wiring, faulty thermocouples, blower motors, and heat exchanger to a qualified Heating and A/C professional; However, there are a few things you may check before contacting an Heating and A/C repairman for furnace service service, saving yourself currency, however one of the most likely reasons your furnace is not working could be dirty or jammed air filters.
A jammed filter can restrict airflow into your system, causing your program to toil harder than it is designed to and ultimately shut down. If the air flow out of your registers or vents seems low, check for jammed filters. Ensure that all your registers are open and not jammed with objects or dust. Not working heating systems could imply faulty pilot ignition light. If your furnace clicks on or initiates the start cycle however fails to fire up, you actually have a faulty ignitor/sensor! Under normal operations, your furnace is prompted by the thermostat to click on. Your ignitor becomes orange hot. It initiates the entire heating process of ignoring your gas and blowing the moderate air into your living space. You may also be dealing with a self-explanatory reason as the power to the furnace is off, causing your furnace not to work. Their circuit breaker may have tripped or a fuse blown. The power switch has to be in the ON position for the furnace to work.