Furnaces, on average, can be expected to last around 15 years. It’s not uncommon for an older appliance to need repairs. But you can avoid sudden failure by recognizing the signs of a dying furnace and replacing it. This can prevent disruptions in heating service and other stressful situations that furnace problems can cause.
First, seriously consider replacing the unit if it is 15 to 20 years old. If there’s a pilot light, your furnace was probably installed more than 25 years ago.
Noticeable signs your furnace is dying include:
Increased Heating Bills
A steady increase in your monthly heating bills is a sure sign your furnace is about to go, especially if you’ve kept up with professional maintenance and have sealed your air ducts. Don’t always automatically suspect the utility company is raising its rates. Over time, the cost of a new furnace can be offset by the reduction in monthly bills.
Count how many times your furnace has been repaired in the last two years—and add up the cost. If a repair costs more than half the price of a new furnace, consider getting a replacement. Or, buy a new one if your furnace has had more than two repairs in the past year.
Furnaces shouldn’t make any substantial noise when they’re turned on. Banging, popping, thumping, scraping, or rattling noises are common as furnaces near the end of their life. If you hear the blower turn on and off a lot, a dying furnace may be the cause. Excessive noise means your old furnace is working harder to heat your home.
Lack of Heating
If your home isn’t reaching the desired temperature, some rooms are warmer than others, or you need to adjust the thermostat often, the furnace may not be providing enough heat or distributing it properly. Another sign of a problem is when your furnace blows cold air, or the airflow is weak. This is often caused by a bad thermocouple or pilot light, which can be quite expensive to fix.
Yellow Burner Flame
Furnace flames should be blue. If the flame is yellow, your furnace may be emitting dangerous carbon dioxide, and fuel is burning less cleanly and efficiently. Any flame color other than blue can signify incomplete combustion or a potential gas leak.
Signs of Carbon Monoxide
Carbon monoxide is odorless, colorless, and tasteless. If your furnace is producing this toxic gas, you may see streaks of soot around it, moisture on windows and walls, or rusting flue pipes. There may also be no upward draft in the chimney. If you notice any of these signs, go outside and call your utility company to shut off the gas.
Dry, Dusty Indoor Air
A poorly performing furnace can cause the air in your home to go stale. You may see more dust, shocks from static electricity, or unhealthy plants. It may also be harder to keep musical instruments in tune.
Health issues originating from old furnaces range from allergies to a dry nose, throat, or skin, to symptoms of carbon monoxide poisoning such as burning sensations in the nose and eyes, headaches, or nausea as well as disorientation and flu-like symptoms. Allergic reactions to dust, mold, or dander can also be traced back to your furnace.