7 minutes read

Troubleshooting a Furnace Blowing Cold Air

Stephen Jabro

Why is cold air coming from my heater?

Is your furnace blowing cold airThe middle of a cold Missouri winter is the worst time for a furnace to break down. Yet the coldest days are some of the busiest for our repair technicians at Jon Wayne Heating & Air. Fortunately, our team has encountered just about every possible problem heaters can have and they can often get a furnace quickly back up and running.

One of the most alarming problems a homeowner can experience is cold air coming out of their vents. It may even seem like suddenly your air conditioner is running. Instead, what is probably happening has nothing to do with your AC and maybe not even your furnace. Fortunately, when a furnace appears to be blowing cold air, it’s a problem that can usually be fixed.

What should you do when you find your furnace is blowing cold air?

Don’t assume the cold air means your furnace is broken. That may be the case, especially if you have an older furnace, but there are a lot of other reasons why there isn’t warm air coming through your vents. And a lot of those reasons are easy for just about anyone to address on their own.

Jon Wayne Heating & Air is here for you whenever you want a professional heating technician to examine and service your furnace. But we do want to arm you with troubleshooting steps that could allow you to save some time and money by avoiding an unnecessary service repair.


Before You Call: The 4 Troubleshooting Steps

There are some basic steps a homeowner can try before calling a professional HVAC repair technician. Most can be done easily and with little or no money.

Thermostat set for 68, something to check when your furnace is blowing cold air


Make sure that your thermostat is set to be warmer than the current temperature in your home. It’s possible someone else in the house decided to lower the setting without you knowing.

Unfortunately, this may be the beginning of the “thermostat wars” that a lot of couples find themselves in. But fortunately, this is the easiest “problem” to fix, at least technically.

SOLUTION: Change the desired temperature to several degrees below the ambient temperature and make sure it’s on the WARM setting. If everything is working fine, your furnace should start up soon.


Is the FAN set to ON? Having the blower running all the time could be what’s causing this problem. If the interior air is already at the desired temperature, the furnace will not be heating, yet that air will still be coming through your vents. And so, compared to the existing temperature, it probably feels cold.

SOLUTION: Turn your fan setting to AUTO. This AUTO setting will have the blower fan running only when the furnace is heating the air.

Dirty air filter can cause a filter to stop blowing hot air#3: CHECK YOUR AIR FILTER

We cannot state enough how important a clean air filter is for your home’s entire HVAC system. It can even cause problems that lead to a furnace blowing cold air.

A dirty furnace filter may be blocking sufficient air flow which can then cause the heat exchanger to overheat. This can cause dangerous problems that may even lead to a carbon monoxide leak, so a furnace may shut off its burners as a safety precaution.

SOLUTION: Check your air filter and change it if it is dirty. That may resolve the problem and get hot air flowing again. It is possible you will still need to reset the furnace to start working again. Because of the potential danger of a cracked heat exchanger, you should call a professional heating repair technician to ensure that the furnace can be turned on safely.

Call Jon Wayne Heating & Air Conditioning for quick 24/7 repair – no matter what day or time – at (417) 831-9500 in Springfield or (417) 466-2515 in the Mt Vernon area.


If you have a gas furnace with a pilot light, you may find that it is not lit. Check where your burners are to make sure there is a flame still burning.

SOLUTION: Relight your pilot light. To do this, turn your thermostat from HEAT to OFF so the furnace won’t come on immediately when you light it. Turn the control knob to be set on PILOT. If the knob was already ON, turn it to OFF and wait about five minutes so that any gas can get cleared out.

Safety Note: If you notice the smell of gas after waiting several minutes, you may have a gas leak somewhere. Do not attempt to light or turn on your furnace if you smell gas. Call a professional technician to come out and ensure it can be relit safely.

After waiting those 5 minutes, turn the knob to PILOT and push it in. You should hear the sound of gas flowing. Put a flame to the pilot opening as you continue pushing in the knob.

When you see the pilot light, slowly release the knob and turn it to ON. Now you can turn your thermostat back to HEAT and should soon feel warm air flowing in your home again.

Jon Wayne Heating & Air furnace repair technician in Springfield, MO

HOMEOWNER DIY vs HVAC Professional Repair

This article covered the easiest steps most homeowners can take to handle a simple problem on their own. If what’s causing your furnace to blow cold air is one of these issues, you’ve saved yourself time and expense by resolving it yourself. But there are a variety of other (and more complicated) things that can cause a furnace to stop blowing hot air.

Other Potential Furnace Problems:

  • If you have an oil furnace, you may be out of fuel
  • There are gaps or holes in your duct work
  • The furnace’s flame sensor or burner may have dirt or debris
  • An electrical problem with the heater’s ignition

If none of these troubleshooting steps fix the problem with your heating system, you may have an issue that requires a professional furnace repair technician. Call Jon Wayne Heating & Air at (417) 831-9500 in Springfield or (417) 466-2515 in the Mt Vernon area. We can repair and service any type or model of furnace or heating system. We have hundreds of positive reviews on Google and are the HVAC team southern Missouri trusts to keep their home warm every winter.

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in Springfield & Mt Vernon

With more than 20 years of experience servicing homes and businesses in Springfield, Mt Vernon and surrounding Missouri communities, Jon Wayne Heating & Air is the company you can trust for professional quality service. With 100s of positive reviews, we are the heating and air company relied upon to provide the most efficient and reliable heating and cooling systems to homes across southwest Missouri.


From the S Kansas Expressway, exit on Bennett St. heading west, then turn right on S. Scenic Ave and we’ll be on your right. Coming from W. Sunshine Street, you’ll take S. Scenic Ave going north and we’re just about a mile up the road on your right at 1324 S. Scenic Ave.

Mt Vernon

We are conveniently located right off Highway 39 on the northeast part of town. From W. Mt Vernon Blvd (Hwy 265), turn to go north on Hwy 39.
You’ll find us just about a mile up the road by turning left onto
Breckenridge Rd.

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    1324 Scenic Ave Ste A, Springfield, MO 65802

    (417) 831-9500
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    726 Breckenridge Rd, Mt Vernon, MO 65712

    (417) 466-2515