10 Red Flags That Indicate Your Furnace May Be Failing

Furnace, HVAC News

Has your furnace been acting strange lately? It’s normal to experience a few hiccups with heating, like erratic temperatures or strange noises. That’s why furnace repairs are so necessary. Giving your furnace the attention it needs can mean the difference between a comfortable winter and a miserable one.

On the other hand, if you’re spending more time servicing your furnace than enjoying it, you may have a bigger problem. When your furnace shows that it’s struggling to stay working, it might be time to turn it in for a new one. But installing a new furnace is a serious investment. It’s essential to make sure that you recognize the right signs that it might be failing. Here are ten red flags you need to look out for to tell if your furnace is dying:

Frequent Service Calls

Constantly having to repair your furnace may be the first sign that it’s failing. If your furnace is always having parts replaced or issues resolved outside of its routine check-ups, you need to consider that there is a more severe problem. Furnace troubleshooting should not be a significant feature of your life. Furthermore, leaving a failing furnace alone can lead to bigger problems down the line, like exposure to gas leaks and exhaust fumes. It might be best to invest in a new HVAC system to prevent these kinds of issues.

Flu-Like Symptoms

If you have had many more instances of cold or flu symptoms than normal in the household, it might be a sign that there is a problem with your furnace. Failing furnaces can leak carbon monoxide, which is a toxic gas. When there is poor ventilation in your system’s exhaust or a leak from the gas heater, carbon monoxide can slowly seep into your living spaces. As this gas builds up slowly, it may make you and the rest of the family occasionally sick. According to the CDC, mild carbon monoxide poisoning creates flu-like symptoms. These include –

  • Weakness
  • An upset stomach
  • Vomiting
  • Chest pains

In higher concentrations, exposure to the gas can even be deadly. If these symptoms have frequently been occurring, there may be a carbon monoxide leak somewhere in the home, causing pockets of the gas to accumulate.

The first step in such a situation is to ensure your safety and the safety of the other residents. After making sure that the air quality is safe, call in a reliable HVAC company to take a look at the issue. Other than examining the furnace, they will need to inspect the exhaust and vents because these parts of the system can also create leaks. An assessment of your furnace will allow the team to understand whether you need repairs or a complete overhaul.

It is crucial to invest in carbon monoxide detectors in your home and office space to avoid the worst-case scenario.

Strange Noises

Hearing strange noises from your furnace or vents can be a sign that something is malfunctioning. For the most part, furnaces will make noses during their operation. However, if you begin to hear unfamiliar noises such as rattles or rolls, it might be a sign that some mechanical elements have come loose. In some cases, these are issues that a technician can easily fix. In others, it is a sign that there is a system-wide issue, such as corrosion. A simple service call can diagnose the health of your furnace and let you know if it is time for a complete replacement.

An Old Furnace

Like your other appliances, furnaces also need to be replaced when they get older. Most heating systems begin to fail after approximately 15 to 20 years of use. It is important to keep track of the age of your furnace. If you installed it yourself, then this can be a simple task. If you found it installed when you rented or purchased your home, do some research with the landlord or the previous owners. You may discover that your furnace is past its due date, which would explain any other strange behavior that it’s been exhibiting.

In cases where it’s hard to get any concrete information about your furnace from anyone, try examining the equipment itself. Most models have a label attached with the relevant information on them.

Although some models can last longer than 20 years with the right maintenance, their efficiency decreases. Replacing such a furnace would improve the efficiency of your heating while lowering your energy costs. It would also be less risky in terms of air quality.

Dry Air

In some cases, the furnace is not the right size for the home or office that it is in. Undersized systems end up running too frequently to maintain the right temperature. Oversized systems have the opposite issue, where they don’t run for long enough. Both cases dry the air out. Apart from replacement, there is no other way to correct a poorly sized furnace.

Flame Color

The pilot light in a well-functioning furnace should be blue and vibrant. Pale or weak flames indicate a problem with the amount of gas burning. If your pilot light is wavy or flickering, the gas may not be thoroughly burning. This could indicate a leak, inefficiency, or another issue. A yellow flame is a clear sign of poorly burning gas. If your pilot light is burning in orange or yellow colors, you should consider having your system checked for blockages. Changes in pilot light color are also signs that carbon monoxide may leak into the vents and not be released safely.

Poor Temperature Control

You may find that your thermostat is no longer functioning like it used to. This could be a sign of a failing system. When some of the rooms in your house stay cold even though others are warm, your heating system might need repair or complete replacement.

Higher Utility Bills

As your furnace gets older, it will lose efficiency. This loss in efficiency will result in higher bills because the system will run more frequently to produce the same amount of heat. This will burn more fuel, increasing your gas consumption. However, even running more often will not completely solve the heat production problem. In this situation, you’re still likely to find temperatures dropping lower or some cold spots throughout your home. This is a significant sign that your furnace may fail and that it’s time to replace it.

It is possible to get a tune-up to solve this issue, and your utility bills may drop in the meantime. However, if you have an old furnace, this is only a stop-gap measure. In the long run, the same problem will continue to crop up until you replace the furnace.


If a technician installed your system improperly, soot would always be a feature in your furnace’s operation. If you’ve noticed excessive soot production, it may be time to schedule a consultation and have HVAC experts assess your furnace installation. If your furnace didn’t always produce soot but has started to create it lately, it may be a sign of failure. This often happens to aging furnaces that are no longer able to burn gas properly.

Moisture Building Up

Maybe you’ve noticed that some of the rooms in your house have moisture collecting on the windows, ceilings, or walls. This might be a sign that there’s a problem with the airflow in the house. Damp air is usually an indicator of problems with the furnace or the vents.

Find out more about how to care for your heating system on our blog.