Keep Your Home Warm (in Winter): How to Resolve a Furnace Blowing Cold Air

In the wintry months, our homes transform into warm sanctuaries where we take shelter from the icy tendrils of the frosty weather outside. The furnace, often unnoticed in its daily endeavors, is the silent warrior that keeps the chills at bay. However, when this sentinel starts dispensing cold air instead of comforting warmth, it’s time for action. A furnace blowing cold air might sound paradoxical, but it’s a common issue faced by many households. In this extensive guide, we shall dissect this perplexing problem and provide you with actionable solutions.

photo: penman brown

Common Culprits: Why is My Furnace Blowing Cold Air?

  1. Thermostat Settings:

The humble thermostat, your furnace’s faithful companion, might be the unsuspecting instigator of the cold air conundrum. If your thermostat fan setting is on ‘ON,’ the fan will keep circulating air even when the furnace isn’t in its heating phase. This can result in the furnace blowing cold air during these intervals.

  1. Fuel Supply Issues:

A furnace is a fuel-driven warrior. It requires a continuous and adequate supply of fuel to keep your home warm. Fuel supply problems can occur due to various reasons like a closed gas valve, a faulty supply line, or even an empty oil tank.

An inadequate fuel supply can hinder your furnace’s ability to generate heat, leading to it blowing cold air. Check your fuel supply lines for any visible issues.

  1. Pilot Light Problems:

If you have an older furnace model, the tiny pilot light plays a significant role in the furnace’s heat production. If the pilot light is out, or not functioning correctly, it can result in your furnace blowing cold air. The pilot light is a small flame that ignites the gas burner in your furnace. If this flame goes out, the gas burner won’t ignite, and hence, the furnace won’t produce heat. In this case, you may need to manually relight the pilot light, following your furnace manufacturer’s instructions.

  1. Overheating:

Your furnace is designed to work hard, but like any piece of machinery, it can overheat if it’s overworked. An overheating furnace will shut off its burners to prevent damage, while the fan continues to run to cool it down, causing the furnace to blow cold air.

  1. Clogged Filters:

Dirty or clogged filters are common offenders when it comes to a furnace blowing cold air. An obstructed filter can make your furnace work harder, leading to overheating, and in turn, causing it to blow cold air.

Resolving the Issue: A Step-By-Step Guide to Warm Your Home

Now that we’ve delved into the potential causes let’s look at the corresponding solutions. Restoring your furnace to its proper working condition may be simpler than you think.

  1. Adjusting Thermostat Settings:

If you’ve found that your thermostat is set to ‘ON,’ and you prefer it to blow only heated air, adjusting the settings is straightforward. Switch the fan setting to ‘AUTO.’ In this setting, the fan will only operate when the furnace is actively heating the air. This simple switch can sometimes resolve the issue of your furnace blowing cold air.

  1. Checking Fuel Supply:

If your furnace isn’t receiving the required amount of fuel, it can’t produce heat. It’s as simple as that. So, what can you do? If you have a gas furnace, make sure the gas valve is fully open. If your furnace runs on oil, check if there’s sufficient oil in the tank.

Remember, dealing with fuel supply issues involves a certain level of risk, especially with gas furnaces, as you’re dealing with flammable material. If you’re unsure about any step or if the problem persists even after checking the fuel supply, it’s safer to call in a professional.

  1. Re-lighting the Pilot Light:

If your pilot light has gone out, you can typically relight it by following the instructions provided by your furnace’s manufacturer. However, if the pilot light won’t stay lit, it may indicate more complex issues like a faulty thermocouple or gas supply issues.

Dealing with the pilot light requires a certain level of understanding of your furnace’s operation. If you’re uncomfortable dealing with it, it’s better to call in a professional. Ignoring a faulty pilot light can lead to inefficient heating and even safety concerns.

  1. Addressing Overheating:

If your furnace is overheating, it needs immediate attention. The first step to resolving this is to replace your dirty or clogged air filters. Clogged filters restrict the airflow, causing your furnace to work harder, leading to overheating. Changing your air filters regularly not only prevents overheating but also improves your furnace’s efficiency and longevity.

  1. Seeking Professional Help:

If you’ve tried all the above steps and your furnace is still blowing cold air, it’s time to bring in the experts. A heating professional has the knowledge and tools to accurately diagnose the issue and suggest the best course of action. Sometimes, the problem could be more complex, involving internal components of your furnace. In such cases, a professional’s expertise is invaluable.


When the harsh winter winds howl outside, a warm, inviting home is the ultimate solace. A furnace blowing cold air can disrupt this tranquility, turning your cozy retreat into an icy cold fortress. But by understanding the potential issues and addressing them promptly, you can restore your home’s warmth. Regular maintenance, timely troubleshooting, and professional help when necessary can ensure a warm and cozy home throughout the winter. After all, winter should be a time for snowball fights and hot chocolate, not troubleshooting a cold-blowing furnace!

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