Why Your Furnace Is Blowing Cold Air
The main function of a furnace is to keep a house warm, and a furnace that is blowing cold air can't handle this function. Knowing why your furnace might blow cold air can help you with the diagnosis if it ever comes to that. Below are some of the common reasons a furnace might blow cold air.
The thermostat serves as the main input for the furnace controls. It receives and sends the signal for the furnace to start heating, and to which temperature. Therefore, thermostat issues can easily make your furnace blow cold and not warm air. Below are some of the specific ways in which this might happen:
- The thermostat is wrongly set – for example, if someone accidentally sets the temperature too low.
- The thermostat's batteries are dead.
- The thermostat's electrical connections are disconnected.
- The thermostat is located near a heat source, and it is registering a temperature higher than the room temperature.
As you can see, various thermostat issues can deny you hot air. Therefore, a cursory inspection of your thermostat should be one of your first steps if you are not getting warm air from the furnace.
Electronic Control Malfunction
Your furnace has an electronic control board that controls most of the furnace's functions. The control board receives feedback from the thermostat and uses the feedback to control the operations of the furnace. Therefore, a malfunction of the control board, for example, due to an electrical fault, can result in the wrong control signals being sent to the furnace. Thus, the furnace might fail to heat your house even if the thermostat is properly set.
Ignition problems can also prevent your furnace from burning fuel and giving you warm air. This can be the case whether you have a modern heating system with an electronic ignition system or a traditional furnace with a pilot light. For example, the electronic ignition system can suffer an electrical failure. The pilot light can go off, for example, due to draft exposure.
Lastly, fuel-related issues can also make your furnace blow cold air. For example, you can run out of fuel if you are using an oil-fired furnace. For a gas furnace, it might be possible that something has affected the supply of gas to your house. In such a case, all appliances that use gas in your house should be off. Or maybe the gas valve, which controls the amount of gas getting into the furnace, has been accidentally maladjusted.
Reach out to a heating contractor if you suspect you need a furnace repair.