It’s the first chilly night of the year, and after you turn on your heater for the first time this year you notice that the furnace starts blowing lukewarm air instead of the warm air that you expected.

Everybody has been there before. At first, you may think the furnace will stop blowing cold air on its own, but after several minutes you realize that something is wrong and that the furnace is not going to fix itself. We will examine the most common issues that cause your furnace to blow lukewarm air, including:

  1. Check your thermostat’s settings.
  2. Check that your filter is not dirty.
  3. See if you own a two-stage furnace.

You and your family deserve to enjoy your time together throughout the year, and that is why we will look over several ways to fix the problem of your furnace blowing lukewarm air. Fortunately, there are four primary reasons it’s happening and you should be able to get your home to a comfortable temperature if you follow these four simple steps.

1. Check The Thermostat’s Settings

Often times your furnace could be running but no heat comes out of your vent because your thermostat is on the wrong setting. This is the most simple solution to fix your heating issues, and you can check this issue by making sure your thermostat is set to “auto” instead of set to “on.”

Your home’s residential HVAC system uses a complex set of sensors to tell the temperature inside of your home. This information helps your furnace determine how much heat it needs to push out based on your thermostat’s setting.

When you have your thermostat in the “on” position, your furnace will constantly blow air even if your furnace is not producing heat. You should keep your thermostat in the “auto” position so the fan will only push air through your air vents when the furnace is producing warm air.

Fortunately, it should be simple to fix this problem quickly. Change the thermostat’s settings until you get the results you want. Move it from “on” to “auto” and the fan will quit when the furnace changes the air to the desired temperature.

If your vents continue to push out lukewarm air even after setting the thermostat on the “auto” position, it’s a good idea to check the limit switch on the furnace. The setting for that should also read “auto” instead of “on” or “manual override.” If you notice it’s in the wrong position, change it back to fix the issue.

If you change this setting on the thermostat and you still feel lukewarm air blowing through your vents then you may have to address some other issues. Now that you have checked the thermostat setting, we will continue on to the next issue for you to troubleshoot

2. A Dirty or Bad Air Filter May Be the Culprit

Air filters improve the air quality in your home, and you need to change your air filters every few months to ensure your HVAC systems work as efficiently as possible. Air filters are essential HVAC parts to keep clean to ensure your furnace pumps out warm air throughout the winter.

Here are some of the most common issues that you should check with your air filters when troubleshooting lukewarm air blowing from your furnace:

  • Check if your filter is dirty. Simply remove the air filter and replace the filter if it is clogged.
  • Check that you have the right air filter. Different HVAC and furnace units need specific air filters. Remove the air filter and check that the filter is made for the make/model of your furnace set up.
  • Check if the filter is pointing the right way. Your filter needs to be pointing the right way to allow airflow to pass through the filter properly. Remove the filter to ensure that the filter is pointing the right way. The filter may be wrong for the furnace so check all the specs.

Having a clean air filter for your home’s HVAC system is important because they do the heavy lifting for air heating and cooling systems. Since air filters stop dust and other particulates from circulating throughout your home, they can become overwhelmed with the constant accumulation of dirt and debris.

It is important to keep your air filters clean because once your filters get clogged you will notice that your HVAC system works less efficiently and will even begin to blow lukewarm air through your vents.

When airflow through your vents are blocked, the burner of your furnace will shut off, while the blowers continue to run as normal. Over a short period, the fan will turn the air cold or lukewarm at best.

Air filters keep the air in your home clean and easy to breathe. If you notice that your vents are blowing lukewarm air during colder weather then you should check that your filters are clean, installed correctly, and the right size for your furnace unit.

3. You Own a High-Energy, Two-Stage Furnace

If your furnace continues to blow cold air then you should check if you have a two-stage furnace. Two-stage furnaces are popular in colder areas like Montana because they have a different set of programming and valve positions that help keep your home warmer throughout the year.

A two-stage furnace has three valve positions (full-open, partially open, and closed) to provide different levels of heat output based on the needs of your home. A two-stage furnace operates at full blast when the valves are fully open, but when they are partially open the furnace will put out 60-65{b23f27e77d506857133c0484664f5e97b9b9607f950df85d319f5db37a0a0ce6} of the full heating potential.

This means that a two-stage furnace has two heating settings that will kick on automatically based on the temperature inside of your home. Since these furnaces in their lower stages of heating don’t push air that’s as warm as the higher stages, you may feel lukewarm air from your vents instead of the high heat that you expected.

The amount of heat your two-stage furnace pushes out is based on how often the thermostat is kicking your furnace on and off. In most cases, the best solution to cold air blowing from your two-stage furnace is to simply wait for the furnace to kick on again to push out the desired amount of warm air.

4. The Trouble Lies with the Gas Supply

Many furnaces are heated by natural gas or propane gas. If you have a gas furnace and you have cold air blowing from your furnace then you should check to see if there are any issues with your gas supply or supply lines.

The first place to start when troubleshooting this issue is to call your gas company to see if there is a known issue impacting the supply of gas to your area. If you notice regular activity like the flames on the burner igniting, the problem is most likely not going to be the gas supply.

There’s also a small chance there’s an issue with the flame sensor or thermocouple. When that happens, you will not see the burners ignite. Observe the process of the furnace turning on and off to see what happens.

If the furnace refuses to light correctly now, it may be a faulty thermocouple or a broken flame sensor causing the problem.

If you have called your gas supplier and there are no known issues, you should contact your local furnace repair professional. We will help you diagnose the issues that you are experiencing, and we will ensure that your family and home are safe while also addressing the problems that prevent your home from warming as expected.

Hire The Best Furnace Team In Billings, MT

Only you can decide if you’re in over your head with solving any of these four common heating problems. If you don’t want to do the work, or if it’s just not in your wheelhouse, leave it to the professionals.

There’s no reason to stress out about a complicated heating issue when you can resolve the trouble fast by reaching out to our HVAC professionals.

Even a relatively straightforward job like changing the air filter can get dicey. If you select the wrong type or size, your HVAC system won’t function correctly.

If you decide to make repairs yourself and still end up having the same problem, you can always reach out to an HVAC professional to get it fixed fast! That way, you’ll be right back to a toasty warm environment in record time.

Contact R & T Services Today!

F.A.Qs For Furnaces Blowing Lukewarm Air

Is your furnace blowing lukewarm air and not keeping your home warm? The most common issues that cause your furnace to blow lukewarm air, including:

  1. Check your thermostat’s settings.
  2. Check that your filter is not dirty.
  3. See if you own a two-stage furnace.
How long do furnaces typically last for?

While the lifespan of a furnace depends on the amount of use, the type of furnace, and other factors, you should expect your furnace to last you at least 15-20 years.

Can a furnace be repaired?

Yes, your furnace can be repaired if it is blowing luke-warm air. You should rely on a local trusted HVAC repair company to help you repair your furnace. If your furnace is less than 10 years old, there is a good chance that your furnace can be repaired if it is blowing lukewarm air.