You have a furnace blowing cold air, which means you are losing money and everyone is bundled up and shivering inside. Sound familiar? A broken furnace is stressful situation that can make everyone's life difficult. You need to call a furnace repair right away before it gets worse or if your furnace won't turn on. In the meantime, you know that this will happen again next year unless something is done! And if you have a heat pump blowing cold air or heat pump blowing room temperature air, learn more about your auxiliary heat here.
Find relief for the present and future. Once you know how to troubleshoot your furnace not blowing hot air, why it happens, and how to keep it from happening again, you'll never be in this situation again. So let's stir up some heat!
First, let's take a closer look at how your furnace works.
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How does A Furnace Work?
Let's talk about your HVAC system's heating cycle.
As soon as the indoor temperature drops below the thermostat's set temperature, the thermostat signals the control board located inside the furnace to begin the heating process. The combustion process begins by turning on the ignition switch, opening the gas valve, and turning on the draft fan. The combustion warms up the furnace's heat exchanger. As a result of the combustion, flue gasses are released outside by the heat exchanger and exhaust pipe. A blower fan drives room temperature air past the heat exchanger. The cool air absorbs the heat and and from there is forced through your home's air ducts. Now you know how the heating process works, let’s investigate what makes your furnace blow cold air.
If you have a malfunctioning furnace, it may be due to a number of causes, and our HVAC experts have seen it all before!
Now, let's get into the top reasons what makes a furnace blow cold air:
Furnace Blowing Cold Air Because Of No Fire
Your furnace not blowing hot air could be due to the ignition failing to start. Without an ignited burners, your home will never get heated up! Now that we know where this problem lies- let's take a closer look at what may disrupt the ignition process.
Bad Thermostat May cause cold air blowing out the vent When heat is on
When it comes to heating your home, the thermostat is a pretty important device. Your thermostat signals your HVAC system to turn on your heat when your home reaches the temperature you set to initiate the heating cycle.
When the heating cycle is turned on, the thermostat sends a message to the circuit control board, located inside the furnace. This involves turning on the furnace blower and the furnace burner. This is where problems can arise. If your furnace is blowing cold air, there is a possibility the thermostat is sending the message to turn on the blower motor, but not the burner. Without activating the burners, the air being blown into your home will not be heated air.
Fixing thermostat
Faulty Circuit Control Board May Explain Heater Blowing Cold Air
In some instances, the culprit could be the circuit control board. Your furnace's circuit control board serves as the brain of the furnace, relaying instructions to its various components. When the circuit control board receives the heating cycle command from the thermostat, it sends out signals to turn on the furnace blower and furnace burner. If the circuit control board is malfunctioning, it could turn the furnace blower on but not the furnace burners. So if your furnace is not blowing hot air, it may be due to the circuit control board not turning on the burners to heat the air.
There are many reasons why a circuit control board can fail, and the most common cause is a lack of cleaning and maintenance. But, take notice if you have a furnace leaking water. Your circuit control board is at immediate risk for permanent damage. The leaking water might be dripping on your circuit control board, corrupting and disabling its electrical components. It's important to fix a leaky furnace before it causes other problems, such as no heat.
control board
Pilot Light going out/ Faulty Electric Furnace Ignition
Your furnace could be blowing cold air because of an ignition problem. If you have a broken pilot light/ electric furnace ignition, there will be no fire to heat the cold air. This feature is a small flame that ignites the burners. If you have a more modern furnace, you most likely have an Electronic Furnace Ignition. Pilot Lights are the standard for older furnaces. If you suspect your pilot light is the reason your furnace is blowing cold air, learn more about why your pilot light keeps going out here.
Gas Furnace Blowing Cold Air From Lack Of Fuel
If your gas furnace is blowing cold air because it fails to ignite, the problem may be with your gas