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Why is My Furnace Blowing Cold Air?

December 29, 2021 | Blog

Although winter in Southern Louisiana isn’t as harsh as other parts of the U.S., we do get our fair share of freezing weather (and sometimes in the form of snow!). The last thing you want to deal with on these days is your furnace blowing cold air and not knowing what to do. At Southern Air South Louisiana, we have compiled a list of some of the most common reasons why your furnace would blow cold air and tips for troubleshooting.

Common Causes

Dirty Filters

The number one cause of a broken furnace is dirty, clogged air filters. This issue should not be taken lightly as the restricted airflow forces your unit to work longer and harder than it needs to. Over time, this can cause your furnace to overheat or even shut down completely!

What to do: The Environmental Protection Agency (EPA) recommends changing your filters at least once a month – or at the very least, every 3 months. Southern Air suggests keeping more than a few filter replacements on hand so you don’t have an excuse to not change them regularly.

Thermostat Settings

The next thing you should check is your thermostat’s fan settings. If you’ve accidentally set your thermostat to ON instead of AUTO, then you might notice your vents blowing hot air sometimes, and cold air other times. The reason for this is, when your thermostat is set to ON, your furnace’s blower fans are running continuously, even in-between heating cycles.

What to do: Simply switch your thermostat’s settings back to AUTO. Your furnace should then only run the blower fan during heating cycles rather than in-between. Also, make sure your furnace is at a high enough temperature to actually turn on your furnace!

Shut Off Pilot Light

Older furnace models have something called a pilot light. This is a small, blue flame located inside your furnace, and it’s used to ignite the natural gas being sent to your furnace’s main burner. When you turn on your furnace, gas is released through a valve, which then comes in contact with the pilot light, producing heat through combustion.

If you’ve noticed your pilot light isn’t turned on, then your furnace won’t be able to warm any air as combustion isn’t taking place!

What to do: Most gas furnaces come with an instruction manual showing you how to relight the pilot light yourself. However, be sure to shut off your furnace for at least 15 minutes as the gas valve that supplies fuel could still be releasing gas. Lighting a match or lighter with a buildup of gas in the area can cause an explosion. Southern Air suggests contacting a professional HVAC technician to assist you in safely relighting your pilot light.

Poor Gas Supply

If your pilot switch is working just fine but you’re still getting cold air, then another cause could be inadequate gas supply. A few reasons why your gas is running low includes:

  • The gas bill wasn’t paid in time
  • Damaged gas valve
  • Disruption on the gas line
  • Gas needs to be refilled (if you use propane instead of natural gas)

What to do: When dealing with anything gas-related, it’s always best to leave it to the professionals. Shut off your furnace and contact your gas company to examine your furnace’s gas supply. In the meantime, use portable space heaters and blankets to keep warm.

Contact Southern Air South Louisiana

If troubleshooting is unsuccessful, then it’s time to call Southern Air South Louisiana to help you uncover the problem. Our HVAC specialists will provide a thorough furnace inspection and cleaning to ensure your furnace gives you no more trouble this winter! We are also providing heating services in Monroe as part of the Southern Air family!

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Arrived promptly. Clearly discussed with me the issue with my unit. Compressor is going bad. Was able to give me quotes for work to be done, when and finance options available including 0% interest for 3 years of I were to replace entire outdoor unit.

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Service is 1st rate as always. I’ve always been satisfied with Southern Air Heating and Cooling South Louisiana. From installing a new heating and cooling system to routine maintenance, this is the company to choose. Highly recommended for all your heating and cooling needs.

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Very efficient. I called at 245pm on a Friday, was told the tech would be at my residence at 4, he was here by 3! He quickly identified and thoroughly explained the issue. Will have to make an appointment for the repairs, however I am confident the job will be done well

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