If your furnace is blowing cold air, you may be wondering why or how to fix it. There are several possible causes of a furnace blowing cold air, so it can be hard to give advice without gathering further information. However, below are some common causes that will cause your furnace to blow cold air.
Thermostat is set to ON position
Is your thermostat set to the ON position instead of the AUTO position? If you have your thermostat set to ON, the blower in the furnace will blow air continuously even when the burners aren’t warming the air, causing cool air to come out of your registers. By setting your thermostat to AUTO, the blower will only blow air when the furnace is heating. Some people choose to leave their thermostat on the ON position as it helps filter air throughout the house.
Your furnace has overheated
So your furnace was blowing warm air, then all of a sudden the air becomes cool for no reason. What’s up with that? It is possible that your furnace has overheated. Your furnace has a safety mechanism built in that monitors temperature and will shut down when it becomes too hot to prevent a fire from starting inside your furnace. The most common cause of a furnace overheating is a dirty air filter. If your filter is dirty, not much air can pass through and in turn, your furnace will start to overheat. Don’t ignore this problem. Repeatedly overheating your furnace will damage your furnace’s heat exchanger which is a very costly fix!
Furnace pilot light is out
Older gas furnaces have standing pilot lights instead of an electronic ignition. If you have a furnace that was installed in 1996 or prior, it’s likely you have a pilot light in your furnace and it may be out, causing your furnace not to ignite. If your pilot light is out, re-light it. If it refuses to light, be sure the gas is on to your furnace and the gas valve on your furnace is set to the on position. Also check to make sure the pilot light is not dirty as that can cause it not to light as well. If your pilot light still will not stay lit, you may have a problem with your thermocouple and it needs to be adjusted or replaced. If you don’t feel comfortable doing this, contact us here and we can help!