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Modern Heating & Cooling

Signs Your Furnace Needs a Replacement

With any other system in your home, it is important to watch for the signs your furnace is going bad, so you know when to call. If you notice these signs that your furnace is going bad at home, let’s chat about your furnace replacement options!

Most of these warning signs apply to a gas furnace, however, many of these signs can be applied to other heating systems. Here is how to tell if your gas furnace needs a replacement vs a repair:

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Increasing illness symptoms

More instances of flu-like or cold symptoms among household members may be due to a carbon monoxide leak in the gas heater or poor ventilation of the exhaust. When carbon monoxide builds up in the home, it affects us and can make us sick in small doses. A carbon monoxide detector is a real help for your home or commercial property, as it’s the only way to detect carbon monoxide leaks. 

Once you have detected carbon monoxide, the next step is taking a look at your HVAC system. The carbon monoxide can come from different sources of the furnace. If the exhaust is not properly controlled and vented out of the living space, the harmful gas builds up.  

High furnace age

If you are suspecting that your furnace is beginning to fail, it might be because of its age. Check the age of your heating system by looking at the information on the label attached directly to the unit. The average age of a furnace is 15-20 years, however, some models last longer with proper maintenance. The issue with heating systems lasting longer is that at 20 years the efficiency of the HVAC system is diminished even if the system still works. Leading to higher energy bills.

Increased heating bills

As your furnace gets older, it loses efficiency, and your heating bills increase as the heating system runs more frequently. This uses more fuel however it does not always mean more productive heat. The heater runs and runs but doesn’t keep the space comfortable, which is one of the signs your furnace is going bad.

Pilot flame color changes

The correct color of a gas furnace is a vibrant or bright blue flame. When the pilot light color changes, this is an indicator that carbon monoxide is not being pushed away from the system as it is supposed to. A yellow flame or when a flame is flickering are clear signs that the gas is not burning properly. Dirty or partially blocked systems can produce this. 


Soot is typically a sign that gets overlooked, but soot can occur from either your system not been installed correctly, or it also can be from an aging system that may need to be replaced. Soot is one of the signs your furnace is going bad.

Read More: Is It A Problem If My Furnace Repeatedly Stops and Starts?

Don’t Ignore the Signs Your Furnace Is Going Bad – Call Now!

The signs your furnace is going bad means it’s time to replace. If you would like to schedule a furnace replacement or speak with a trusted, award-winning, local HVAC company, give our heating and cooling experts a call. 

Modern Sheet Metal provides furnace and air conditioner service, repair, replacement and installation throughout Appleton, Neenah, Menasha, Darboy, Kimberly, Kaukauna and Greenville. Please call us at 920-733-4713 to discuss your residential or commercial heating & cooling needs!