Loud furnace noises can happen for all kinds of reasons. Whether it’s a problem with the fan or unburned oil built up in the box chamber, furnace noises can signify more serious problems. Older furnaces are more likely to start making these noises, so when you hear them contact a furnace repair professional immediately. This will prevent potentially dangerous situations and save you from even more expensive repairs in the future.

Loud Scraping Sound

If you hear a loud scraping noise that sounds like metal rubbing on metal or nails on a chalkboard, this probably means something is wrong with the furnace’s blower wheel. When you hear this noise, turn off your furnace immediately and call a professional.

The three most common problems with the blower wheel are:

  • The wheel came loose from the motor shaft is now hitting the blower casing
  • The wheel is broken and needs to be professionally replaced
  • The motor mount is broken and causes the blower to drop and hit the housing

Banging or Popping When the Furnace Turns On

Dirty furnace burners: The dirt on the furnace burners delay them from igniting and cause an excess of gas to build up. When gas does finally ignite, you will hear the loud bang. Never ignore this noise because small explosions can crack the heat exchanger. Consistent maintenance can help prevent this problem before the heating season starts.

Expanding and contracting air ducts: This commonly happens when you have metal ducts. Ducts expand and contract as the blower turns off and on, which can be a sign of undersized ducts, closed vents, flimsy ducts or a clogged air filter.

Squealing or Whining

High pitched squealing noises are caused by one or more of the following:

  • Loose, slipping or fraying blower belt
  • Shaft bearings that need oil
  • Malfunctioning blower motor

The squealing or whining noise isn’t as problematic as the other issues, but it should be fixed before it causes any further trouble. An annual furnace maintenance visit can prevent the belt from slackening or certain parts become under-lubricated.