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Why Is My Furnace Blowing Cold Air?

“Why is my furnace blowing cold air?” It’s a question that many homeowners find themselves asking — usually on the coldest nights of the year. 

If your furnace is blowing cold air in your home, it may be an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. You can quickly solve some of these issues by cleaning or replacing components in the furnace. 

A furnace blowing air but no heat in your home is a headache you don’t need. Johnson & Johnson Heating and Air Conditioning is your team of experts in furnace repair in Martinsburg and Frederick to keep your home comfortable year-round.

We’re here to answer questions about gas, oil, electric furnaces, and other heating topics. But first, let’s cover a few possible causes for a furnace blowing with no heat and a few steps for fixing the problem.

Possible Reasons a Furnace Is Blowing Cold Air

Damaged Pilot Light

When your furnace blows cold air, it’s a good idea to check the pilot light in your gas system to ensure it’s working correctly. The pilot light in your gas furnace should ignite the burners to deliver heat. In particular, older gas furnaces commonly have issues with the pilot light. 

In this situation, you want to relight the pilot:

  1. Find the pilot light assembly and reset toggle.
  2. Move the reset toggle to the off position to shut off the gas supply.
  3. Wait a few minutes to allow excess gas to leave the chamber in your furnace. 

Next, adjust the reset toggle to the pilot setting to allow gas to flow to the pilot light. After changing this setting:

  1. Locate the reset button on your furnace.
  2. Hold it down.
  3. Place a match in front of the pilot light.

You should see the formation of a flame from the pilot light. Once you see a flame, release the reset button. You’ve successfully relit the pilot light, which should get your furnace blowing hot air again.

Dirty Flame Detector

Some other types of gas furnaces don’t rely on a pilot light to activate the heating process. Instead, furnaces without pilot lights rely on flame detectors to ensure the successful operation of the heating cycle. 

If your flame detector gets covered in dirt, dust, or grime, it will lose its ability to produce heat for your heating system. Cleaning the flame detector should fix this problem. Another option is to call a professional HVAC technician if you’re uncomfortable with the process. Johnson & Johnson Heating & Air Conditioning has experts ready to help you. Contact us if you need any assistance.

Low Gas Supply

If you’re not getting heated air in your home, it may be an issue with the gas supply line in your home. A lack of sufficient gas will deactivate your furnace by design. A furnace needs a certain amount of gas to perform its usual heating functions. 

Calling a professional HVAC company is the way to solve this issue. A furnace not blowing hot air because of a gas supply issue is a repair you’ll need a professional to make.

Clogged Air Filter

A clogged air filter may be another cause of a furnace blowing cold air. When your furnace’s air filter accumulates dirt, dust, and grime, it blocks incoming air from reaching your gas furnace. In addition, furnaces that have overheating issues or run on long heating cycles may have dirty air filters.

We recommend replacing the dirty air filter with a new one to solve the problem of a furnace blowing but having no heat in your home. Additionally, the new air filter won’t block airflow to your gas furnace, so overheating shouldn’t be an issue. 

Damaged Ductwork

If you’re wondering why your furnace is blowing cold air, it may be a result of cracks and holes in your home’s ductwork. These openings range from large to small and let cold air from your attic enter your air ducts. Your thermostat is set to auto, and your furnace is blowing warm air, but it may leak out before it reaches the vents.

This situation isn’t a furnace repair problem but a ductwork repair one. Duct sealing will allow the warm air to reach the vents more easily. 

Johnson & Johnson Heating and Air Conditioning Has You Covered

Why is my furnace blowing cold air? If you’re asking this question, Johnson & Johnson Heating and Air Conditioning can diagnose and repair the problem. If it’s an easy fix, we can provide you with advice for fixing it on your own. 

Is your furnace old and in need of replacement? We offer furnace installation in Martinsburg, Frederick, and beyond. Contact us today to request an appointment with an HVAC expert!

This image shows a woman bundled up in winter clothing as the result of a cold house.

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