3 Furnace Noises You Shouldn’t Ignore

Chances are you don’t give your furnace much thought—until it stops working. Fortunately, your heating equipment is likely to emit one or more warning signs to let you know that a repair is imminent, and knowing what to watch for can mean the difference between a minor fix, and a more costly repair. Among the most common symptoms of a failing furnace are unusual sounds, which differ from the everyday noises typically associated with startup, or the hum of the motor. While most noises are completely benign there are some that you shouldn’t ignore, including the three sounds listed below.


Once the thermostat sends a call for heat, your furnace springs into action. Fuel is sent to ignite the burners, and once they are lit heat production begins. If you hear a loud bang, boom, or popping sound as your furnace starts up it’s imperative that you pinpoint the source and hire a professional to resolve the issue. Causes may include:

Duct expansion – A loud banging noise that originates several feet away from the furnace is likely caused by the expansion and contraction of metal ductwork due to fluctuating temperatures. As the furnace blower cycles on and off the metal heats and cools and the laws of physics are applied, but excessive expansion and the ensuing noise can be a sign of one or more issues which may require the attention of a professional. Causes may include:

  • Clogged air filter
  • Closed vents
  • Inadequately installed or poor quality ductwork
  • Undersized ducts

Dirty furnace burners –  A dirty or neglected furnace can cause a number of issues, including delayed ignition from an accumulation of dirt on the furnace burners. In the time it takes for the dirt to burn away, gas fumes can build up in volumes significant enough to cause a small explosion when lit—threatening the integrity of the heat exchanger. As part of routine heating maintenance, the technician will inspect, tune, and clean your furnace, including the burners.


If you hear a sharp squeal or whine coming from your furnace it warrants further investigation, and may be caused by:

  • A blower belt which has deteriorated, is slipping, or has become loose
  • A failing fan mower
  • Shaft bearings that require lubrication


The sound of metal on metal is an indication that there is an issue with the blower wheel. Allowing the furnace to run can result in significant damage, and the unit should be switched off at the first sign of noise, and a technician called for immediate repair.

Common issues with the blower wheel include:

  • A broken motor mount, which is designed to hold the blower assembly in place
  • A broken blower wheel
  • A loose blower wheel, which has become separated from the motor shaft; the noise may be caused by the wheel hitting the casing, and if no major damage has occurred, the technician may be able to simply tighten the wheel back up

Call BVS Heating, Ventilation & Air Conditioning for Furnace Repair or Replacement in Katy, TX

Trust the experts at BVS for high quality, reliable furnace services including furnace installation, maintenance, or repair. Call us today at 281-391-1510 to schedule an appointment, or contact us online and let us know how we can help.

Author Bio:

Ronald Via

Ronald is one of the key contributors to BVS Home Experts, a family-owned and operated full-service air conditioning and heating company serving the Katy and West Houston areas. With a deep understanding of air conditioning and heating concerns, Ronald brings a wealth of knowledge to our readers.

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