Top Reasons That Your Furnace is Blowing Lukewarm Air

For home heating in Texas, furnaces tend to be among the most common systems. Their extreme affordability and versatility of fuel options make them the perfect solution for most homeowners throughout the state. Unfortunately, just like any other heating system, a furnace can experience issues from time to time. One of the more common ones is that it produces lukewarm air. Below are some of the top reasons this problem pops up, along with expert tips on what to do to solve each one.

It’s Still Warming Up

It’s not uncommon to experience lukewarm air coming out of your ducting when your heating system first kicks on. Air has to travel through your cold ducting to reach the different rooms of your home. So, until that ductwork warms up, heat from the air will dissipate into the ducting. It’s best to give your heating system 5 to 10 minutes to warm up. If you’re still experiencing lukewarm air after 10 minutes of your system running, there’s an issue somewhere else.

Incorrect Thermostat Setting

The fan on your thermostat can be set to on or auto mode. When in auto mode, the blower fan will only run whenever your heating system runs. If the blower fan is set to on, it will continually run around the clock until you manually shut it back off. You may be experiencing lukewarm air coming out of your vents because your blower fan is running, but your heating system is not.

Essentially, the blower fan circulates warm air from your home in and out of the ductwork. Take a moment to check your thermostat settings and switch your blower fan to the auto setting. The fan should immediately turn off if your heating system isn’t running. Give it a few minutes and wait for your heating system to kick on for its next cycle. The blower fan should kick on when your furnace does and produce warm air from your vents.

Dirty Air Filter

Your furnace has a built-in filter that removes unwanted airborne contaminants. This helps enhance indoor air quality and prevent unwanted debris from entering your furnace. Unfortunately, if you don’t regularly keep up with filter changes, your air filter could get so dirty that it restricts airflow throughout your ducting. When your furnace struggles to pull air throughout your ductwork, you will experience less heat from your air vents.

It’s best to pull out the furnace’s air filter and check to see if you can look through it. If you can’t, the air filter is full of debris and needs to be replaced. Be sure to put in a filter of the same size to ensure it will be effective. Make it a habit to check the filter in your furnace at least once a month, and always have an extra filter on hand if it needs to be replaced. In addition to annual furnace tune-ups by an HVAC professional, filter changes are the number one maintenance task that you can do yourself at home.

Ducting Leaks

If you’ve noticed that your heat has been diminishing over weeks or even months, the culprit could be your ductwork. As the metal of your ductwork experiences temperature fluctuations, it will expand and contract. Eventually, unwanted air gaps will develop as the air ducts start to pull apart. Unfortunately, this can allow a lot of your hot air to seep into your wall and floor cavities instead of making its way to the rooms in your home.

If you think there might be leaks in your heating or cooling ducts, it’s a good idea to have a professional take a look. They can use specialized tools to seal up your ducting to eliminate those unwanted air gaps. This will allow all the hot air that your furnace produces to effectively reach all the rooms in your home.

Blocked Ductwork

Another reason you may only be getting some hot air out of your ducting is that you have a blockage in your ductwork. This blockage could result from dirt and other debris entering your ducting over many years and never being thoroughly cleaned. In other cases, the blockage may be due to a pest infestation where they’ve built a nest inside your ducting.

Either way, it can be helpful to have a professional assess the interior of your ducting to determine if there is any blockage and have them remove it. Once the blockage is removed by a duct cleaning expert, the airflow in your ducting will return to normal, and your furnace should deliver adequate heat from all of your air vents.

Heating Elements

If you have an electric furnace, it has multiple heating elements that heat the air as it passes over them. If one of your heating elements goes bad, your electric furnace will produce less hot air. Even a faulty heating element that’s only half working can also disrupt the heat your furnace produces.

If you suspect a heating element issue, you should call an HVAC technician to assess the issue further. In most cases of faulty heating elements, they can simply replace them so your furnace can return to producing adequate heat for your home.

You Have a Two-Stage Furnace

Many newer high-efficiency furnaces have a built-in two-stage function to help optimize their operating efficiency. As a homeowner, you will notice a stark difference between the two different stages of heating. When your furnace needs to heat your home a lot, it works harder and uses its maximum heat setting. This is when it produces the most warmth to help balance out the big difference in temperature. However, if it only needs to compensate for a slight temperature difference, it will run in its low mode.

In this low operating mode, you’ll notice that the air from your vents is closer to lukewarm than extremely warm. If you have a high-efficiency furnace with two stages, there’s likely nothing wrong with your furnace. You can test it out by simply increasing the temperature on your thermostat by a few degrees. This will cause your heating system to switch from low to high heating mode. Within a few minutes, you should notice a stark difference in the temperature of the air coming out of your vents.

Faulty Ignition Components

Another reason that you may be experiencing lukewarm air coming out of your ductwork is that you have a faulty ignition component in your furnace. When your furnace is trying to start and fails, the blower fan will still be on, circulating the warm air in your home throughout your ducting. Take a look at your furnace and see if it’s lit. If it isn’t, the problem could lie with the gas supply line, the flame sensor, or the electric igniter. It’s best to have one of our HVAC technicians evaluate this problem further to identify the root cause of the issue.

Reliable Furnace Repair Service

Lightfoot Plumbing, Heating, Air & Electrical offers reliable furnace repair service for the Weatherford, TX area. We’re a full home services provider and in addition to providing comprehensive heating services, we can help with all your air conditioning, plumbing, and electrical needs. We are your local HVAC and plumbing installation, repair, and maintenance experts. Call us today to book your next service appointment with one of our HVAC technicians or plumbers.