Furnace Not Blowing Hot Air? Here Are 10 Reasons | Service Emperor

Property owners in the US and Canada count on their furnaces to provide warm air through the cooler months. Unfortunately, sometimes an electric, propane, or gas furnace starts blowing cold air.

Furnace not blowing hot air and live in Savannah, Pooler or the surrounding area? Our team at Service Emperor can help you go over the causes for this HVAC issue and provide service to get your furnace working properly again. Contact us at (912) 231-5430 to set up an appointment.

For everyone else, keep reading to find out the top 10 reasons why your furnace isn’t blowing hot air. 

#1: Thermostat Issues

Thermostat issues often cause problems with your heating system. HVAC professionals frequently identify four issues tied directly to the thermostat.

  • The thermostat batteries died.
  • Someone changed the temperature settings.
  • The thermostat’s fan setting is on.
  • Someone installed the thermostat improperly.

Even a low battery may prevent the thermostat from transmitting your commands to the furnace. Check your battery, and ensure the thermostat setting is correct. Then see if those two actions get the system blowing hot air again.

Sometimes a homeowner gets a thermostat recalibrated by a professional. However, sometimes you can address the problem by adjusting an auto setting or turning off the fan switch.

#2: You Have Clogged Air Filters

Furnaces heat your home by circulating hot air through your HVAC system of ducts. The air passes through an air filter that removes contaminants like pollen, pet dander, and dust. A clogged filter stops air circulation, leading to furnace issues.

Fortunately, you can address problems caused by a dirty filter in a few steps. Visit your local home improvement store and purchase a replacement air filter for your furnace. Change a dirty air filter regularly to prevent problems with air flow.

Want help with a dirty air filter? Contact an HVAC professional to let a skilled technician change the furnace filter for you.

#3: Clogs in the Condensate Lines

Condensate lines remove excess moisture generated by your HVAC system in the summer months. Unfortunately, grime and dirt often gather in these lines, eventually leading to a clog that prevents the channels from draining appropriately.

Clogged condensate drain lines cause the float switch to flip in your furnace. Once the switch flips, it shuts down your system, preventing your furnace from blowing warm air.

Regular furnace maintenance helps you avoid this issue. Technicians perform a thorough cleaning on the lines as part of our maintenance service, getting rid of clogs before they can develop.

#4: Lack of Fuel

If your furnace is not blowing air, take a moment and ask yourself if the system has enough fuel to operate. In our busy world, many homeowners forget to check their natural gas supply or oil levels.

A furnace without enough fuel cannot distribute warm air, even if all components remain in good repair. Make sure the furnace has an appropriate gas supply or that your oil tanks remain full before you try to operate your heating system.

What about electric furnaces? They require access to electricity to function. Make sure the circuit breaker has not tripped and that you turned the furnace switch to “on.” An HVAC expert may also check your blower motor panel to ensure the furnace blower gets sufficient power.

#5: High Limit Switch Failure

Dirty filters sometimes cause your furnace to overheat repeatedly. Repeated overheating can cause the furnace’s high-limit switch to fail. This failure causes your furnace to think that system is constantly overheating.

The furnace responds to a broken high-limit switch by deciding to blow cold air constantly. Avoid this issue by taking steps to prevent frequent overheating. Homeowners often have trouble diagnosing this problem on their own.

#6: The Pilot Light Went Out

This problem applies only if you have a gas furnace. Gas furnaces use a pilot light, just like you’d expect to see on a gas stove. Without the pilot light, the furnace won’t even turn on to heat your property.

Excessive air movement may cause a pilot light to blow out, especially with an older furnace. You should be able to check and see the pilot light. If it went out, relight it, or contact an HVAC technician for assistance.

#7: Dirt on the Flame Sensor

Gas furnaces also have numerous safety measures, including flame sensors. Manufacturers place the flame sensor in the burner assembly. It works by detecting the presence of a flame inside your furnace.

The sensor shuts off your furnace as a safety measure if it cannot detect a flame. However, a dirty flame sensor sometimes shuts down the heater because it can no longer “see” the flame. This sensor stops your system from putting warm air out, leaving you with cold air in your home.

Maintenance crews know how to clean your sensor quickly to get the system working correctly so you don’t feel like you’re getting air conditioning in the winter.

#8: Burner Clogs

Your furnace relies on a burner to generate heat. The fuel may be gas or oil. If you notice cold air blowing through your home, you could be facing a clogged burner.

Burner clogs prevent the combustion required to generate heat. However, they don’t stop the fan from blowing. Therefore, you may end up in a cold air dilemma with your furnace appearing to run but producing no heat.

The heat exchanger in your furnace operates close to the burner. Over time, wear and tear damage the heat exchanger, leading to issues. A cracked heat exchanger may prevent your furnace from working correctly. Furnace repair experts step in to clean your burner to get your furnace blowing hot air again.

#9: Faulty Gas Valves

Did your gas furnace start blowing cold air unexpectedly? The issue could relate to the furnace’s gas valve switch and gas valves and not enough gas is flowing. Gas valves deliver fuel into your existing heating system, allowing the furnace to operate and raise your air temperature.

These valves wear out over time or develop clogs due to debris gathering in the lines. Avoid feeling like you’re getting air conditioning when you want heat by setting up regular appointments to have your gas valves cleaned and maintained.

#10: Outside Air Entered the System

Sometimes, cold air enters your system through cracks or damaged ducts. Your duct system should be contained, keeping warm air in and cold air out. Damage to the ductwork lets your heat seep out into surrounding areas, making it feel like the air conditioning is on.

Avoid cool air when you want warmth by having professionals assess your system. HVAC crews repair cracks and leaks. You can work with the professionals when installing a new furnace to ensure that they install any necessary additions to your ductwork.

Contact Us If You Have a Furnace Blowing Cold Air

Do you feel like you have a fan blowing air conditioning when you want warm air? If so, reach out to our professional team at Service Emperor. We provide service appointments if you have an old or new furnace. Allow us to assess your concerns and perform any necessary repairs. We work quickly and always put you first.

Reach our team by calling (912) 231-5430.

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Tersh Blissett

CEO of Service Emperor and part-time HVAC Guru

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