Why Is My Furnace Blowing Cold Air? Part One

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Nearly half of American households use natural gas for heating, and as temperatures plummet, the use of the home furnace rises. And just like other home appliances, a furnace requires care or issues can arise. One of the most annoying of which is when the furnace blows cold air instead of warm, comforting air.

It has been common for those who experience this issue to replace their heating system with a newer model, but this isn’t always the best solution. When your furnace blows cold air, diagnosing why and resolving it is often cheaper than a full replacement and can aid in preventing future potential issues.

So why might a furnace blow cold air and how can it be fixed?

Thermostat Issues

A thermostat controls the furnace temperature, so if it isn’t working, the furnace won’t work properly. Possible thermostat issues include:

Dirty Thermostat: Dust can build up on the thermostat and cause heat transmission issues by blocking the thermostat’s vents, and sometimes- the gauge. When this happens, your thermostat cannot offer the heating you expect in your home.

programmable thermostat
    • Solution: Use a soft cloth dipped in cold water to clean the thermostat. Avoid using lots of water on the thermostat component because you might cause a permanent problem. If you find this process tedious or difficult, contact us to help you.
  • Improper Installation: Homeowners often attempt to DIY installation of furnaces and other HVAC systems and components, which can lead to improper installation. A thermostat that is not well installed cannot work well. It must fit in its exact location for it to provide heat.
    • Solution: Confirm the thermostat is well located in its respective place. If the wires are loose, fix them. Once installed properly, limit the number of people who touch it. Children and inexperienced persons may uninstall it and cause more problems.
  • Incorrect Thermostat Settings: Thermostats have multiple setting buttons. Some control the fan, while others regulate the heat you get from it. The commonly used buttons on the thermostat are ON, AUTO, and OFF. Choosing “ON” for the furnace only makes it run, it doesn’t necessarily tell it to expel warm air.
    • Solution: Switch your thermostat from the ON mode to the AUTO mode. The furnace should start to blow warm air unless there is another underlying problem. You can later switch to the ON mode when you get enough heat in the house.
  • Old Thermostat: Old thermostats have many operational problems when compared to newer ones. If your thermostat has been in use for more than a decade, then it’s old and could be malfunctioning.
    • Solution: Replace it. There are many smart thermostats on the market now. They are efficient and easy to use, and adjust. Just ensure you choose the best compatible thermostat for your system. You may have to involve an expert in the process to avoid making mistakes.
air filter

The Air Filters Are Dirty

A thermostat is not always the cause of your furnace issues. Sometimes, the problem could be caused by your filters. Filters allow the air needed by the furnace through for combustion. But sometimes the air that feeds in the burner system can be filthy with dust, debris, and other sorts of dirt may find their way into the filters. If you don’t replace or clean the filters often, they may become heavy with dirt and affect the quality of the warm air you get.

Solution: Remove and replace the dirty filters (or clean them if they’re reusable). The cleaning process should be gentle, and you should not use corrosive cleaning agents. If you’re using a reusable filter, but it is too old or the holes are too big, then consider a replacement. The average cost of replacing the filter ranges from $4 to $11, and you can carry out the replacement process independently.

There Isn't Enough Gas

If the furnace doesn’t have gas to light, there will be no heat. Thus, cold air blows instead. Consider that during the summer months when you weren’t using the furnace, the gas valves may have closed, broken, or clogged. Closed or clogged valves cannot supply gas to the furnace, and this translates to cold air.

Solution: Open the gas valves and confirm there is enough gas for the combustion. If you use a personal gas tank and it’s not empty, then check the gas’s pressure. The normal gas furnace pressure should be more than 15%. Any percentage less than that isn’t enough for heating.

If you use a shared gas line, check with your neighbors to confirm that the general gas line is working well and is not turned off. The furnace should work well once the gas line is turned on if this was the main cause of the cold air.

Issues With the Computerized Controls

All furnaces made in the last few years come with computerized controls. The manufacturers fit them with self-diagnostic technology, which users should master before using the furnace. Although each brand is unique, the general concept is the same. When the furnace detects a problem, it displays an error code. The owner then checks what the error code signifies so the issue can be addressed.

Solution: Use your manufacturer’s handbook to learn how to use the computerized controls. Check the meaning of each error code and how you can solve it. With that information, you’ll know how to handle common problems affecting your furnace. The information may also advise how to avoid cold air and what to do should you experience it.

The Pilot Light Is Off

Older furnaces often utilize a pilot light (a flame) to heat the air. When the light (flame) is out, the furnace will continue blowing air, except now it isn’t heated first. For those with modern furnaces- those without a traditional pilot light- this issue may prove tricky.

Solution: Relight the flame by checking the bottom part of the furnace and locating a small knob. If you can’t locate the knob, check the manufacturer’s handbook for guidance. The knob contains three main settings: ON, OFF, and PILOT. Tap the OFF option and wait for at least 5 minutes to ensure that no gas is coming out. Afterward, tap the PILOT option to switch on the gas and restart the pilot light.

Once it’s on, you can now tap the ON option to ignite the pilot light. If the pilot lights remain off and the air remains cold, there may be an underlying issue. If you experience this, contact us to inspect the furnace and recommend an ideal solution.

For those with furnaces without the traditional pilot light- i.e. they use an electronic ignition, which includes the hot surface ignition, please note that many of electronic ignition systems aren’t long-lasting, which means if it isn’t working, it likely needs replacement. And if your furnace is more than four years old, you may consider replacing the entire pilot light if you suspect that ignition issues are behind the cold air.

Furnace Still Blowing Cold Air? Contact an HVAC Professional

Are you still getting cold air from your furnace? Check out Part Two of “Why is My Furnace Blowing Cold Air?” for more ways to troubleshoot, or skip it and get help from Phoenix Air ATX

Most of these issues are not serious, and you can eliminate them if they’re caught and resolved early. So, don’t dump your furnace or suffer in silence. Contact Phoenix Air ATX take care of your furnace maintenance, repairs- and if needed- furnace replacement or installation.

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