Why Is My Furnace Blowing Cool Air?

 

Have you noticed your furnace is running, but the air that’s blowing out of your vents seems cool? There are several possible causes for a furnace blowing cold air, but the following are 5 common causes you can often fix yourself.

 

Thermostat Set to “On”
Check your thermostat and make sure it is set to “Auto” rather than “ON.” When your thermostat is set to “ON”, the fan on your furnace will blow continuously, even when the furnace isn’t actually heating your air.

 

Dirty Air Filter
A dirty air filter restricts your airflow, causing the furnace to stay on longer in order to heat your home. This can eventually cause your furnace to overheat and shut down the burners to prevent major damage. Make sure you are checking your filters on a monthly basis to ensure cleanliness.

 

Your Pilot Light Is Out
If you notice your pilot light is off, relight it. What is a pilot light? A pilot light is a small gas flame, usually natural gas or liquefied petroleum gas, which serves as an ignition source for a gas burner.
Usually, the instructions on how to do this are on the furnace. If they are not, try looking it up in the manual that came with your furnace.

 

If the pilot refuses to stay on, make sure gas is flowing into the furnace. Make sure the gas valve is in “ON” position. If the switch is in “ON” position, see if your pilot light is dirty. If this is the case then clean it so that gas can come through again.

 

If the pilot lights but will not stay lit, then you likely have a problem with your thermocouple. This may mean your thermocouple may need to be adjusted or replaced. If you have never done this before, we recommend contacting a professional.

 

Inadequate Gas Supply
The gas supply running through your furnace might have been cut off. This will not allow your furnace to receive the gas needed to supply the warm air you need.

 

Damaged Ducts
Warm air travels through your ducts when being distributed through your home. If your ducts are torn or damaged the treated air will never reach it’s intended location. Furthermore, if your ducts are torn, filthy air from your attic or crawlspace may infiltrate your air distribution system, and you would be effectively bathing in dirt and debris.

 

Detecting damaged duct work can be easy, unfortunately repairing them requires an expert. Should you have any questions or concerns about HVAC system, feel free to give us a call. We’re here to help the residents of Rancho Santa Margarita, Trabuco Canyon, and Orange County 24/7.

 

FOR MORE TIPS VISIT OUR PAGE “WHY HEATERS FAIL” > 

2 Comments on “Why Is My Furnace Blowing Cool Air?

  1. Thanks for the advice about looking in the manual if the instructions to light the pilot light aren’t on the front of the heater. The temperature where I live dropped to 30 degrees yesterday and my furnace is blowing cold air. If I can’t find the instructions in the manual, I think I’ll call a heating repair service so I can warm up my house.

    1. Hannah,

      Some furnaces have electrical iginition systems which do not require a lit pilot. Do you have any idea what the age of your furnace might be?

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