It's the middle of winter, and you're ready to turn on your furnace. However, when you do so, nothing but cool or tepid air comes out. Your furnace seems to be all in order and is running smoothly, but still, you've got no heat. There could be several reasons for this happening, most of which are easy to examine. Here are some things to check if your furnace is not blowing out hot air.
Your Filter Needs Changing
Dirty air filters block airflow through the system and cause your furnace to overheat. Many furnace systems have a safety feature that shuts off the burners if this happens. Turn off the furnace, change the filter, and wait until the unit cools before restarting.
Your Fan Is Set to "On"
Many systems have a fan-only setting that blows air continuously even when the heat is off. That means you will feel cool air flowing from the vents from time to time. If you want to remedy this, then put your setting on "auto" and both fan and heater will run at the same time.
Your Thermostat Is Wrong
Your thermostat could be broken or reading the wrong room temperature. You may have a faulty temperature sensor that's sending false readings. You could also have a dead battery or a short in the thermostat's wiring.
You Have No Fuel
If you have oil or gas heat, then you may have run low or completely out of fuel. If you feel it's too soon to run out of fuel, or you run on a municipal gas supply, then you could have a leak. Some units are designed to shut down if the gas or oil supply is inadequate.
Your Ducts Are Leaking
Your unit could be blowing out cool or tepid air because heat is escaping through leaks in the air ducts. Sometimes, air ducts pull or break apart and need repair. When this happens, you may find yourself turning up the thermostat to compensate. If the ducts are in really bad shape, then you will not have enough heat entering your room. Call a furnace repair contractor if this seems to be the case
If you have checked all these, and everything is fine, then it's time for professional help. You could have an internal mechanical or electrical problem that only a professional can diagnose. A licensed technician will not only re-check all of the above but open up your system to get to the root of the problem. Call a heating company as soon as possible to get started on having heat again.