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Why Is My Furnace Blowing Cold Air?

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Did you turn the furnace on, expecting nice warm air before being met with stale cold air?

Your heating system giving up on you is already problematic, but unreliable heating during winter is on another level. You can expect a midseason breakdown if you have missed a few routine maintenance services.

dirty air filter, mechanical failure, and clogs in your air ducts can damage your furnace's heat exchanger.

Keep a watchful eye on your HVAC systems. Your furnace blowing cold air can make winter days intolerable.

So, why is your furnace blowing cold air?

Why Do Furnaces Blow Cold Air?

A furnace blowing cold air may stem from compromised components, especially those critical to the heating cycle. The heating cycle requires critical components to work consistently and cohesively.

Potential reasons behind your malfunctioning furnace include but are not limited to the reasons listed below:

  • Dirty air filters
  • Gas supply leaks
  • Flickering pilot lights
  • Clogged condensate drain lines
  • Insufficient fuel supply

Cold air coming from your air ducts can come from minor to more significant issues. It is hard to pinpoint one reason against endless possibilities when your heating process is compromised.

Remember, the failure of one vital element can kickstart a domino effect. Finding the source may help you save the rest of your critical components.

Should I Worry if My Furnace Blows Cold Air?

Yes. Cold air blowing through air ducts may be the beginning of worse problems. If your furnace blowing cold air has become increasingly unbearable, we should get to the bottom of things.

You can call an HVAC technician to help locate the source, but it helps when you know things firsthand. A less-than-reliable HVAC professional may provide you with subpar HVAC services.

Improper services are one way to ensure your heating system overheats or succumbs to the pressure of external temperatures. Don't settle for cheap services!

Schedule a pre-season maintenance service to prevent a broken furnace from being your stick in the mud this winter.

Is Your Furnace Blowing Cold Air?

It doesn't take a furnace technician with an extensive background to know when your furnace is blowing cold air. If your furnace is producing cold air, there will be a chill in the air.

Your heater blowing cold air causes a draft in the room. A draft that may be harder to ignore than the one coming from an open window. It may cause shocking dips in your home's temperature.

When the thermostat fan setting is set to its highest possible capacity, your air ducts blowing cold air may lower ambient temperatures faster, especially when it's equally cold outdoors.

You may also smell unusual odors coming from your air vents. Dirt buildup within air filters may sully your air quality. If your air filter isn't clean, expect stale and smelly cold air.

There are various possible underlying causes. Don't forget to check electrical links and pipelines when you inspect your furnace.

The Most Common Causes Behind a Furnace Blowing Cold Air

You can always call an expert for assistance. Still, it may help to know a thing or two about these threats against your HVAC system.

Here are some of the most common causes behind your furnace acting unusually.


Clogs disrupt everything. Sediment buildup in pipelines hinders airflow, preventing elements from getting where they need to go. If there's a clog anywhere in your furnace, it may lead to unusual activity.

Clogged Condensate Line

Some furnaces have lines that facilitate water. Condensate lines transmit water or condensation away from the furnace.

Clogged condensate lines may mishandle water flow, failing to extract condensation. Enough water clogged in your condensate line may lead to backflow, impacting critical components in the combustion process.

Clogged Filter

Air filters trap impurities and pollutants to prevent contamination. A furnace filter doesn't filter your ambient air.

A furnace filter purifies air intake before turning it into heated output. The internal air filter prevents particles from getting into the furnace.

Pollutants getting into the furnace can penetrate the furnace's heat exchanger. A dirty air filter allows particles into the heat exchanger and disrupts ignition.

The blower fan may not stall and continue to facilitate airflow. Without ignition, the only air blowing through your furnace will be cold air.

Fuel Supply

Furnaces use various fuels to power heating. Your heater blowing cold air may result from a lack of fuel intakes, such as gas, oil, electricity, or air.

Inadequate Gas Supply

A furnace burner typically initiates combustion by firing up a fuel source. If you have a gas furnace, remember its gas supply.

Gas furnaces can't alter room temperature air without the pilot light firing up the gas supply. A dirty air filter can suffocate ventilation, preventing your gas supply pipe from sending resources into the furnace burners.

If the furnace is blowing cold air, inspect the gas valve and open it to release the supply. Your furnace can't deliver hot air when the pilot light doesn't have the resources to ignite.

Poor Electrical Connections

It isn't only natural gas furnaces that require fuel intake. Your furnace blower, motor, flame sensor, and heat exchanger may all require electricity to produce hot air.

Your thermostat setting may also be incapable of transmitting commands properly due to electrical issues. Electricity plays a significant role in all furnace systems.

All furnaces require some fuel to ensure the pilot light burns continuously. A steady supply of fuel helps furnace burners generate heat according to your thermostat settings.

There may only be a loose stitch in the wiring that requires tightening to continue producing warm air. However, there may be worse problems if everything is intact and your air vents continue to blow cold air.

Pilot Light

The pilot light is the key to all ignition. It is the most critical step in the heating cycle.

A flickering or faulty pilot light may render your gas supply and other resources useless. Even a surplus of fuel can't give you warm air without the pilot light.

Faulty Thermocouple

A thermocouple is a safety feature that acts as a flame sensor. It facilitates different elements through temperature readings. The thermocouple is linked to the pilot light and gas valve.

The thermocouple prevents the pilot light from starting up when it doesn't detect any hot air within the burner chamber. Cool air saturating your furnace disrupts the thermocouple's functions.

Poor Pilot light assembly

Different sensors and burners comprise the pilot light assembly. When one component is amiss, the rest cannot function adequately.

A dirty filter may also lead to a buildup of residue within the thermocouple. It may hinder its sensitivity and hinder combustion.


A valve, output, or supply pipe leak can domino into the rest of the furnace. Leaks anywhere in the furnace almost always warrant maintenance services.

Leaks in your valves may prevent external controls from ensuring the loosening or tightening of the corresponding internal components.

Leaking Ducts

Air leaks in your ductwork may also allow cold air to contaminate heat distribution. Unreliable duct sealing allows heat to escape and makes distribution a struggle.

Your furnace blowing cold air may be a ducting issue rather than warrant furnace repair. Air vents blowing cool air may be remedied by insulation and tightening.

Still, it's a problem that needs immediate attention, hopefully before your furnace overheats.

Installation & Maintenance

Don't underestimate minor furnace issues as one-offs. A dirty valve is one thing. Still, more underlying issues may be beneath the surface.

Without proper installation and maintenance, your furnace's thermostat signals may never be adhered to. Only entrust reliable furnace experts for installation and maintenance.

Improper Installation

Installing heating and cooling systems isn't easy. Many measurements and calculations are involved to ensure the security of your HVAC systems.

When it comes to these sophisticated systems, there's very little margin for error. A pipe one degree off its supposed configuration may throw the whole system.

Poor Maintenance

Maintenance cleaning and tune-ups range from replacing an air filter to tightening the blower wheel. There are plenty of components that require professional services.

While you can find affordable air filters on your own, replacing old ones may require more skills and experience. You may cause more problems than just your furnace that blows cold air.

The Proper Care and Maintenance of Your Furnace

Thanks to routine care and meticulous installation, your furnace may be more energy-efficient and provide sustainable heating.

Finding the root cause may help you avoid worse damage that warrants costly repairs in the future. You may also prevent your HVAC system from sustaining irreparable damage.

Still, you shouldn't just "wing" a furnace repair. There are reliable people with the right expertise for the job around Oregon.

Need Help? Call Sunset Heating & Cooling | Electrical

If your furnace isn't blowing hot air, we have just the guys for you. Call Sunset Heating & Cooling for emergency furnace repair and other heating services.

We can get an HVAC professional on your doorstep in no time to get your furnace blowing hot air again. Don't wait for winter.

Let's get down to business now.

Call now at (503) 500-5866

What Our Clients Say

Sunset went out of their way to help with my project and David was amazing. Great job and look forward to future projects.

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Roman did an awesome job. I had the trifecta, new AC unit ,furnace and hot water heater. Courteous, and competent service. I highly recommend Sunset Heating & Cooling.

-Charles E.

Eduardo provided excellent service when he repaired our AC. I felt his effort was over and above expected. Polite and professional at all times. Good job!

-William G.

Caring, professional and helpful. Thanks for making things happen quickly and getting my Dear friend's heating back up and running in such a quick manner. You went above and beyond for a family in need and that is very much appreciated. Thanks from the whole group!

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