5 Signs Your Furnace Is About to Fail
As the vibrant greens of a Missouri summer give way to the crisp, cool air of autumn, our attention inevitably turns indoors. We look forward to the comfort of a warm, cozy home, a safe harbor from the impending chill of winter. The unsung hero of this seasonal comfort is the furnace, humming away quietly in a basement or closet, faithfully keeping our families warm. It is a piece of equipment that is all too easy to ignore, until the day it stops working.
A furnace failure rarely happens without a warning. In the weeks and months leading up to a complete breakdown, a struggling system will almost always send out distress signals. These signs can be subtle at first—a slight change in sound, a small increase in your utility bill—but they are the early warnings of a much bigger problem on the horizon. Learning to recognize these signs is the key to taking proactive control of your home’s comfort and safety. It allows you to address a potential issue in the calm of fall, rather than being forced to make a frantic, expensive decision during a no-heat emergency in the middle of a Chesterfield January cold snap.
Sign #1: The Age of Your Furnace
The single most reliable predictor of a furnace’s future is its past. While modern furnaces are built to be durable, no mechanical system lasts forever. The average lifespan for a residential furnace is typically between 15 and 20 years. If your furnace is approaching or has already surpassed this age milestone, it is living on borrowed time, and you should be especially vigilant for any signs of trouble. You can usually determine the age of your furnace by finding the manufacturer’s label on the unit, which often includes the installation or manufacturing date.
A furnace in the Chesterfield area works incredibly hard every winter to combat the freezing temperatures, and this consistent, heavy workload takes a toll on its components over the years. Even if an older furnace seems to be operating without any obvious issues, it is important to consider its declining efficiency. A 15-year-old furnace, even one that was top-of-the-line when it was installed, is significantly less efficient than a new model. Continuing to operate an aging system means you are paying more than you need to on your monthly utility bills.
Thinking about your furnace’s age is about proactive planning. It is far less stressful and more cost-effective to research and schedule a planned furnace replacement in the fall than it is to be forced into a hasty decision when your house is freezing and you’re facing an emergency. If your furnace is in its golden years, it is time to start considering its retirement.
Sign #2: Strange and Unusual Noises
A healthy, properly functioning furnace should operate with a consistent and relatively quiet hum. You will hear the clicks of ignition and the gentle whir of the blower fan, but these sounds should be familiar and unobtrusive. When your furnace begins to make new, loud, or startling noises, it is communicating a clear message: something is mechanically wrong. These sounds are not normal signs of aging; they are symptoms of distress that should never be ignored.
Different noises can point to different problems. A loud banging or popping sound, particularly when the furnace first kicks on, often indicates an issue with delayed ignition. This means gas is building up in the combustion chamber for a moment before it ignites, creating a small, forceful explosion. This is not only jarring but can also place stress on the system’s heat exchanger. A persistent high-pitched squealing or screeching noise is a cry for help from the blower motor. This sound is frequently caused by a worn-out or slipped blower belt or, more seriously, failing bearings within the motor itself. If left unaddressed, this can lead to a complete and costly failure of the blower motor.
A rattling or rumbling sound can sometimes be as simple as a loose access panel, but it can also be a sign of a much more serious issue. Rattling could indicate a problem with the burners or, in a worst-case scenario, a cracked heat exchanger. Paying close attention to the new language your furnace is speaking can provide critical clues about its health. Any new and persistent noise is reason enough to have a professional technician from Lolich HVAC perform a thorough inspection.
Sign #3: Rising Energy Bills and Decreased Efficiency
One of the most subtle, yet telling, signs of a failing furnace is a slow, steady increase in your monthly utility bills. The furnace may still be producing heat and keeping your home comfortable, but it is having to work much harder and run for much longer to do its job. This decline in efficiency is a natural consequence of age and wear and tear on the system’s components.
As parts like the blower motor, ignitor, and gas valve age, they lose their peak operational efficiency. The system as a whole has to compensate, meaning it will run for longer cycles to bring your home up to the temperature set on the thermostat. You may not notice the longer run times, but you will certainly see the result on your monthly gas or electric bill.
A valuable exercise for any homeowner is to compare their energy bills from the current heating season to the same months from the previous one or two years. Barring any major changes in energy prices or your personal habits, your bills should be relatively consistent. If you notice a clear and sustained upward trend in your energy consumption during the winter months, it is a strong indicator that your furnace is losing its battle with age and is becoming an energy drain. This is often the point where the long-term energy savings from a new, high-efficiency furnace begin to outweigh the cost of continuing to operate the old, inefficient one.
Sign #4: Problems with Air Quality and Comfort
Your furnace does more than just heat the air; it plays a vital role in filtering and circulating the air throughout your entire home. When your furnace’s health begins to decline, the quality of your indoor air and your overall comfort can decline right along with it.
If you begin to notice that the air in your home feels increasingly dry or stagnant during the winter, or if you see a noticeable increase in the amount of dust settling on your furniture, your aging furnace could be the culprit. An older system with a struggling blower motor may not be able to circulate air effectively through the filter, allowing more dust, pet dander, and other airborne particles to remain in your living spaces. This can be particularly troublesome for family members with allergies, asthma, or other respiratory sensitivities.
In some cases, you may see physical signs of poor performance, such as soot or dust collecting around your heat registers. This indicates that the furnace is not burning its fuel cleanly or that it is distributing dirty air from the system or the ductwork. Another common comfort complaint is the development of uneven heating, where some rooms feel warm and cozy while others remain stubbornly chilly. While this can sometimes be a ductwork issue, it can also mean that your furnace is no longer powerful enough to produce and circulate the volume of warm air needed to heat your entire home effectively.
Sign #5: The Telltale Signs of a Cracked Heat Exchanger
Of all the potential furnace problems, a cracked heat exchanger is by far the most serious and dangerous. The heat exchanger is a metal component within your furnace that separates the combustion process—the actual fire that heats your air—from the air that gets circulated into your home. It is the critical barrier that keeps your breathing air safe and clean.
Over thousands of cycles of heating up and cooling down, the metal of the heat exchanger can become brittle and develop cracks. When this happens, it creates a pathway for dangerous combustion gases, most notably the deadly, odorless gas carbon monoxide (CO), to leak directly into your home’s airstream. This is an immediate and life-threatening safety hazard.
While a crack can only be definitively confirmed by a professional inspection, there are several telltale signs to watch for. These include a change in the color of your burner flame from a steady blue to a flickering yellow or orange, the appearance of soot collecting inside the furnace, or visible rust and corrosion on the exterior of the furnace. The most critical warning of all is a triggered carbon monoxide detector. Every home with a fuel-burning appliance must have working CO detectors. If your detector ever goes off, you should evacuate your home immediately and call for emergency service. Due to the extreme danger it poses, a cracked heat exchanger is a problem that almost always necessitates a complete and immediate furnace replacement.
Your furnace is an incredibly complex piece of machinery, but it will almost always let you know when it is in trouble. By paying attention to its age, listening for strange new noises, monitoring your energy bills, and being aware of changes in your home’s air quality, you can catch a problem long before it leaves you in the cold. These warning signs are your opportunity to be proactive, not reactive.
The transition to cooler weather is the perfect time to have your heating system professionally inspected and serviced. An expert assessment can diagnose any underlying issues and give you a clear understanding of your furnace’s health. If you have noticed any of these five signs, or if your furnace is simply getting on in years, contact the trusted professionals at Lolich HVAC. We can provide a thorough inspection and honest advice to ensure your Chesterfield home is safe, warm, and ready for the winter ahead.