Signs Your Furnace May Not Be Working Properly

Furnace repairs can be expensive, and replacement is a major expense. Especially if your furnace is older, it’s important to pay attention to signs that could indicate your system isn’t working properly. Improperly functioning furnaces are typically highly inefficient, but they can also be very dangerous. Here are some signs that your furnace isn’t working the way it should, and you should call an HVAC professional right away to ensure that it’s operating safely and at its maximum efficiency.

Old Age

If your furnace is older than ten years, it’s more likely to start needing repairs. The average furnace lasts between 10 and 20 years, depending on the brand and model. Typically, a furnace that is on the verge of failing needs more than one repair during the last two years of its life. For peace of mind and efficiency, consider replacing your older furnace with a newer, higher efficiency model.

Red, Yellow, or Green Flame

The flame on your gas furnace should be present only on the burner, and it should burn blue. If the flame is burning yellow, red, or green, it may indicate that something besides fuel is burning, or it could signal a dangerous carbon monoxide leak due to incomplete combustion.


You shouldn’t be able to smell your furnace after the first couple of days of the heating season. If you smell gas at any time, leave the house immediately and call 911 or your gas company’s emergency number. Gas leaks pose a risk for explosions. Musty odors that persist after the first few days of operation could indicate the presence of mold and bacteria, which may occur when your furnace isn’t working properly. A hot electrical smell may indicate overheating.


Furnaces make noise, but there are certain sounds that could indicate a serious problem with your system.

Booms may be attributed to expanding ducts, but they can also signal a defective gas valve. If your furnace rattles, you may have a loose or worn out belt on the blower fan motor. Clicking sounds may indicate loose bolts on the cabinet or a cracked heat exchanger. Squealing and groaning might result from dirty or worn out motor bearings, and chirping sounds may indicate loose motor mounts.

Erratic Cycling

If your furnace seems to be cycling too frequently, you may simply have a dirty air filter. Regular filter changes are essential for preventing overheating and related damage. If the filter is clean, the frequent cycling may be related to a problem with the thermostat or the blower motor.

Low Comfort Level at a High Price

If your energy bills seem higher than they have in the past and your comfort level seems lower due to cold or hot spots in your rooms, you may need to have your furnace replaced or repaired.

Dry Air & Dust

Your furnace is largely responsible for removing dust and contaminants from your home’s air and helping to keep humidity levels in the optimum 30 to 50 percent range. If your house seems drier and dustier than normal, has more static electricity, or your wood furniture and musical instruments are cracking or drying out, your furnace could be the culprit.

Preventing Problems

The number one reason for furnace failure is lack of maintenance, including neglecting to replace the air filter when it’s dirty. Annual preventive maintenance on your furnace by a qualified professional is essential for extending its operating life, ensuring safe operation, preventing common problems, and maintaining its highest possible level of efficiency.

For more information about whether your furnace needs repairs or replacement, or to schedule your annual tune-up, please feel free to contact us at Comfort Control, Inc.

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