Why Is My Furnace Making Noise?

Furnace making noise? More than just annoying, a noisy furnace could be a sign of a serious problem. How can you tell issues with simple solutions from the scary? Gas-fired furnaces are tricky and dangerous beasts, so it’s never a good idea to go sleuthing with your toolbox. Instead, let your ears point the way to potential trouble so that your description can help a professional quickly, safely isolate the issue.

Why is My Furnace Making Noise?

  • Loud Boom
    A loud boom, bang or pop may be the result of fuel igniting following a delayed ignition. When ignition is late, an excess of fuel builds-up in the combustion chamber, belatedly igniting to spectacular effect and transmitting the noise throughout your home. If you think you hear this even once, call a pro out ASAP.
  • Rumbling
    Persistent, low rumbling indicates an issue with the burner. Turn off your furnace and contact a professional as soon as you notice constant rumbling.
  • Banging
    Loud banging sounds when the blower motor is running often indicates a broken/disconnected component. Turn off your system, to be safe, and call a pro. This could result from an array of causes, including closed vents, clogged filter, bent sheet metal, undersized ducts, loose motor mounts, misaligned blower, or simple expansion/contraction with temperature fluctuations.
  • Rattling
    Rattling may also indicate a disconnected component, or possible a failing motor. Typically, the louder the rattle, the more serious the issue.
  • Thumping
    Thumping/vibrating typically result from a damaged/unbalanced blower wheel or motor. Turning off your system until it can be inspected can help you avoid further furnace damage.
  • Humming
    If your furnace is experiencing issues, that humming noise may be the result of a bad interior fan, failing capacitor, or bad motor. Humming noises in a properly functioning furnace indicate a loud transformer. The holiday season is a great time for an electrical safety inspection – when was the last time you had one?
  • Scraping
    Scraping, metal-on-metal sounds are commonly seen with a loose or broken blower wheel, or broken motor mount. In either case, turning off your furnace and enlisting professional help early can prevent further furnace damage.
  • Thwapping
    A fast ‘thwap-thwap-thwap’ while the blower is running is typically from something stuck in the blower blades or housing.
  • Squealing
    A brief squeal at startup is normal. However continual screeching could indicate a loose fan belt, motor bearings in need of oil, failing compressor or malfunctioning blower motor.
  • Clicking
    Clicking when the system turns on/off is normal. If the sound repeats, however, you may have a bad relay.
  • Whistling
    Whistling typically indicates duct leaks, which are more quickly/easily found by a pro.

Why Furnace DIY Doesn’t Fly

Thinking of tackling furnace troubles yourself? Gas-filled furnaces pose fire and burn risks, as well as emit toxic, odorless carbon monoxide combustion gases. Diagnosis and repair of these noises is best left to a trained HVAC professional for the safety of your family and home.

Furnace talking to you? Stop hitting "ignore!" Ensure the safety of your home and family, protecting the lifespan of your furnace, with the help of Aire Serv® today.