Why Is My Furnace Blowing Cold Air?

By June 22, 2021No Comments
furnace blowing cold air

Those who have a furnace in their home often make extensive use of it during colder months. They might also find themselves in an unpleasant situation if they encounter issues with its heating capabilities.

If you discover your furnace blowing cold air, there is a handful of different factors that could serve as the root cause. Let’s explore everything you need to know about them.

Valve Issues

Occasionally, the source of the issue could lie entirely with the valve of the furnace. The most common reason behind why this occurs is a buildup of debris.

If it’s been a while since you last cleaned your furnace valve, you may find that it becomes difficult to operate. Fortunately, this issue is relatively easy to fix. Thoroughly cleaning the valve is often all that it takes.

Malfunctioning Flame Sensor

In general, you likely have flame sensor issues with your furnace if you find that it initially blows warm air but then quickly begins to blow cold air. As with a furnace valve, a buildup of dirt or debris could interfere with the sensor’s ability to function correctly.

Fortunately, this means that you may be able to resolve the problem by cleaning as opposed to replacing or repairing it. If you find yourself in the above scenario but cleaning does not stop the issue from occurring, you may need to get in touch with a professional.

Thermocouple Problems

For those who are unaware, the thermocouple is a sensor that is responsible for controlling the ignition and gas valve of the furnace. As you might guess, thermocouple issues can easily result in your furnace beginning to blow cold air.

In some cases, all you will need to do is slightly adjust it in order to get it working correctly. If you find that it has become damaged, however, it will need to be replaced.

Clogged Oil Filters

For those who have an oil-fired furnace, it’s not uncommon for the oil filter to eventually become clogged with debris, grime, or dirt. When the filter does not function correctly, it can have an adverse effect on the ignition of the furnace.

In turn, this can cause it to blow air that is much colder than it should be.

As with the above scenarios, a thorough cleaning may alleviate the problem. Oil filters that have become significantly clogged need to be replaced, and you should never attempt to do so on your own unless you have the required level of knowledge.

Your Oil Tank Is Empty

You can’t expect your furnace to get hot without a sufficient level of fuel. This will prevent the furnace from lighting appropriately and cause it to consistently circulate cold air instead.

This should be one of the first attributes of your furnace that you check if you discover this issue. Unlike many of the other complications, it’s highly improbable that you need to make any repairs in this scenario.

Additionally, it may be worth keeping oil stored away within your home garage so that you can refill the oil tank of your furnace when required.

Duct Leakage

Although not quite as common, it’s entirely possible for duct leakage to be the culprit behind the cold air from the furnace. To clarify, let’s assume that there is physical damage (such as holes) throughout the ductwork of your furnace.

As air blows, it may begin to leak out.

If the damage is significant enough, this could result in the air blown throughout your home becoming cold. It is unlikely that most homeowners are able to resolve this issue on their own.

So, it’s in your best interest to reach out to a professional in order to receive assistance.

Electronic Ignition Problems

Newer furnaces tend to have electronic ignitions. However, this comes with a particular risk that many homeowners are unaware of.

There is a chance that you may need to adjust your system from time to time in order to keep it operating correctly. Similarly, parts of your electronic ignition could fail and cause your furnace to blow cold air.

This is yet another complication that you should not attempt to resolve on your own.

Thermostat Issues

Ironically, many people tend to neglect that their thermostat could be responsible for the cold air they experience in their homes. One of the most straightforward reasons behind this scenario could involve someone having switched your thermostat to ‘ON’ instead of ‘AUTO.’

If this were to occur, the fan would continuously operate without ever producing any heat.

Although less common, another possible cause could be the fact that your thermostat is not compatible with your heating system. This is an issue that homeowners often encounter when they attempt to install a thermostat on their own.

If you had the same thermostat for an extended period of time, you may need to replace the battery in order to have your system operate normally again.

A Furnace Blowing Cold Air Needs Attention

In some cases, it may need professional service in order to function correctly. You can use the above information to determine the reason behind a furnace blowing cold air. Then, you can make the decision that’s best for you.

Infinity Texas Air prides itself on its customer service capabilities. Our professional HVAC repair team goes above and beyond for each and every customer that we interact with. We proudly serve Forney, Texas, and surrounding areas, including:


  • Crandall
  • Dallas
  • Forney
  • Garland
  • Kaufman


Want to learn more about what we have to offer? Feel free to get in touch with us today and see how we can help.