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Why Is My Furnace Blowing Cold Air?

Why Is My Furnace Blowing Cold Air?

February 20th, 2023


Do you have a furnace that only sends out cold air? That’s no good, and if you expect to enjoy the rest of the winter season and the unpredictable early fall, you’ll want to have this problem fixed right away.

It does pay to think first about why the situation is happening. We don’t recommend you try to fix the furnace on your own—please don’t open up the furnace cabinet and poke around inside. But there might be a simple error you can correct yourself. In other cases, you’ll need to call a professional HVAC contractor like us for furnace repair in Roswell, GA to get your heat back. Let’s look at some of the possibilities so you’ll have a better idea of what you need to do.

Thermostat issues

One of the first checks to make when your HVAC system is only blowing out cold air when it should be heating is to see if the thermostat is set correctly. It might be set in “fan only” mode so the heating never comes on, or to cooling mode so the AC comes on instead of the furnace.

You may also find the thermostat isn’t responding, leaving your HVAC system stuck in whatever mode it was in last. You can try replacing the batteries (if the thermostat uses them) or call for technicians to repair the unit.

Failed ignition system or a failed pilot light

Modern furnaces use electronic ignition systems to fire up the burners. If the igniter on your furnace fails, the blower won’t activate and you won’t get any heat. Ignition systems need professionals to replace them. For an older furnace, the pilot light may have gone out. You can try to relight it. If it won’t relight, please call for professional repairs.

Faulty flame sensor

The flame sensor detects if the burners ignite when the heating cycle starts. If it doesn’t detect flames, it will shut off the burners to prevent unburned gas from flooding the combustion chamber. The sensor can become dirty, in which case it will incorrectly register that the burners haven’t been lit and will shut them down. HVAC technicians can clean off the flame sensor to ensure that it both works safely and will allow the burners to turn on.

Clogged condensate lines

If you have a high-efficiency condensing furnace, it may shut off the burners if there’s a blockage in the condensate lines that remove moisture from the second heat exchanger. Technicians can clean these lines to get the furnace working again.

Gas supply problems

Natural gas may not be reaching the burners and this will also cause the furnace to shut down and leave you with just a fan circulating air. As with anything connected to a natural gas line, you should never attempt to repair this yourself. Leave the work to our licensed and experienced technicians. 

We are here to ensure you have your furnace fixed and working safely. Our goal is to earn your confidence and trust with old-fashioned values of hard work and honesty.

Dayco Systems has been Metro Atlanta’s choice for more than three generations. Contact us for all your HVAC needs.