The Furnace Is Blowing Cold Air: A Troubleshooting Guide

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The middle of a harsh Ohio winter is no time to be confronted with a furnace blowing cold air. You want to curl up in a cozy house after you deal with harsh weather conditions, so it’s time to take a look at the reasons the furnace may be blowing cold. Some issues with the heat are easy to fix, but others require a qualified professional to get you away from the space heater and back to a house that’s warm all over.

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Check the Thermostat Fan Setting

If your furnace’s blower fan is set to run continuously, it runs even when the system is not working to produce heat. Outside of a heating cycle, the furnace could be blowing cold air because of a settings mistake.

Go to your thermostat and take a look at the fan setting. Make sure the switch is set to AUTO, not ON. With the AUTO setting chosen, your furnace should only run the fan during a heating cycle and not push cold air through your vents in between.

Thermostat Not Working

Since your thermostat communicates your home’s temperature needs to the furnace, if it isn’t working correctly, your furnace could blow cold air because it isn’t receiving the proper instructions from your thermostat.

Replacing your thermostat ensures accurate communication with your furnace to stop cold air issues. Have your thermostat replaced by your HVAC technician, and consider upgrading to a programmable or smart thermostat for better control over indoor comfort and energy consumption.

Check Furnace Air Filter

A dirty air filter hinders air movement through the furnace. This raises temperatures inside the furnace, and the limit switch shuts heating cycles down if the unit becomes too hot. If you have a dirty filter, replacing the filter typically stops cold air from blowing.

  • Find the filter compartment on your furnace, remove its access door if applicable.
  • Slide out and dispose of the old filter.
  • Insert a new one of the same dimensions into the filter compartment. Make sure you follow the directional markings noted on the filter frame for proper positioning.
  • Replace the access door to the compartment, if applicable.

Once the furnace cools down, it should restart. If it doesn’t, you may need HVAC repairs to reset the furnace’s limit switch.

Broken Furnace Control Panel

When a furnace blows cold air, there may be an issue with the unit’s electronic control panel. This is sometimes easily solved by resetting the system.

  • Turn off power to the furnace at its ON/OFF switch.
  • Wait a few minutes, then flip the switch to ON.

If this does not correct the problem, call for furnace repair.

Pilot Light Is Out

If your furnace’s pilot light goes out, the furnace will blow cold air because fuel combustion is not taking place. The pilot light needs to be relit to burn fuel and heat your home.

  • Turn off power to the furnace.
  • Locate the pilot light assembly and turn the reset switch to OFF.
  • Wait 10 to 15 minutes to allow any escaped gas to clear the area.
  • Turn the reset switch to PILOT. While doing so, use a lighter or match at the pilot end to light outgoing gas.
  • Once the pilot is lit, turn the switch to ON.
  • Restore power to the furnace.

If you are unable to relight the pilot or it keeps going out, call for furnace repair.

Standing Water Around Unit

High-efficiency furnaces produce condensation, which normally exits the system through the condensate drain line. If there is a blockage in the line, the system’s overflow kill switch turns off the unit to prevent water damage. Standing water around the furnace is a sign of a condensate line blockage.

Clear condensate drain clogs with these steps:

  • Turn off power to the unit at the breaker.
  • Locate the condensate drain pan.
  • Remove water that sits in the pan with a wet/dry vacuum. 
  • Remove and clean the pan with mild dish soap and water, then replace.
  • Follow the condensate drainpipe that extends from below the pan to its exit outside your home.
  • Attach your wet/dry vacuum to the opening to suck out clogs.
  • Restore power to the unit.

Leaking Ducts

Sometimes, a furnace blows cold air due to duct leaks. Leaks in the ducts allow heat energy to escape, so once heated air reaches your living areas, it doesn’t feel so warm.

Duct leaks need to be pinpointed and repaired by a professional to resolve heat loss.

For Furnace Repair in Cincinnati, Turn to Apollo Home

If your furnace is blasting cold air and troubleshooting does not correct the problem, it’s time to contact Apollo Home to schedule furnace repair. Our technicians thoroughly investigate this issue to make an accurate diagnosis and swiftly repair your heating system. Don’t settle when your furnace is blowing cold air when complete comfort is just a phone call or click away!

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"Ernie & Mike did a superb job on my new furnace and A/C installation. Despite having more than a day’s work to do, they came in and stayed until the job was done. They were organized, efficient, and protected the rest of the house well. Got both furnace and A/C installed the same day. Ernie was courteous, informative, and clearly knew his job better than anyone I’ve encountered before. The units look so good guests now get The Tour of our new system. Apollo is clearly not a fly-by-night company. I would recommend them to anyone in need of a new furnace and/or A/C."
- Jerry A.
"I called Apollo because of a water leak I thought I had in our upstairs shower going into the kitchen. Robbie came and assured me everything was fine & looked at all the other plumbing. He ended up changing a few pipes for our washer & clearing a drain. He was very nice & knowledgeable with all my questions. I ended up signing up for the care plan & was very happy with my service."
- Cassandra B.
"The team at Apollo exceeded my expectations. As a business owner, my attention to the details and commitment to providing excellent service is high. From the sales rep. to the installation team, everyone’s performance was outstanding. For example, the installation team went to great lengths to protect our floors, placing floor runners and across the wood floors and up the stairs. They even were spot washing walls upon their departure. I highly recommend this company."
- Randy B.
"We scheduled an estimate AND a tune-up. We knew something was wrong with our furnace, but hoped we could make it through the rest of the season. Upon telling Bill what our furnace was doing, he warned us immediately what the possible outcome was going to be; a cracked heat exchanger. He watched the flames roll backward, tested carbon monoxide levels, which were so high they meter’s last reading was 5,600 before saying “high”. He immediately shut it down, tagged it, and explained that with levels that high and children in our home he wanted off right away. He continued his inspection and showed us via a camera that not only was it cracked in multiple places, but had holes all over it. He gave us a few options for repairing it; his knowledge as well as genuine concern was beneficial and refreshing. Luckily we also scheduled an estimator, Micah, to come too and we were able to get costs between repairing and replacing (with several options). We decided to replace with a much higher efficiency furnace and one sized properly to our home. Hands down, not only did they both provide us great service and knowledge, but without sounding dramatic, they may have saved our lives. This was our first time calling Apollo, but it won’t be our last."
- Sarah B.
"Apollo is an excellent company. I always receive great service. Alex A. was professional and friendly. He kept me informed during the process of checking my furnace and heat pump to make sure they were working properly. The company makes sure you are notified who is coming and when they are on the way. All my interactions with the company have been wonderful."
- Beverly S.



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