While the familiar sounds of your furnace operating may bring comfort, a furnace making loud noise is downright startling. A far cry from a soothing low hum, loud furnace noises can signal that something may be amiss. We’ll help you troubleshoot a furnace that’s buzzing, rattling or even screeching to quiet the noise.

How to Fix a Furnace Making Loud Noise

As alarming as loud noises can be, a furnace making loud noise doesn’t always indicate a serious problem. Sometimes a simple fix can bring a return to silence. We’ll help you figure out what might be causing loud furnace noises and what type of repair they may require.

Furnace Making Rattling Noise

Oftentimes a furnace making loud rattling noise indicates a loose screw, panel, or duct. We suggest taking these simple steps to stop the rattling:

  • Turn off power to the furnace
  • Tighten any loose screws on the furnace panel
  • Apply duct tape to any loose pieces of ductwork
  • Restore power

If these measures don’t silence a rattling noise we recommend that you contact a professional service to assess the problem. A damaged heat exchanger can also make a rattling sound. If the heat exchanger is cracked or leaking it could emit dangerous carbon monoxide. Contact your local service provider right away to evaluate the situation.

furnace making loud rattling noise

Image from The Family Handyman


Furnace Making Buzzing Noise

A furnace making buzzing noise could have several causes. Here are some possibilities to consider when you hear a loud buzzing from your furnace:

  • Loose transformer box: a furnace transformer reduces your home’s electrical voltage for the furnace to use. The transformer box can loosen over time and buzzing noise from the box may result. Simply tighten any loose screws on the box with a screwdriver. If this doesn’t stop the buzzing, a transformer may need to be replaced.
  • Faulty capacitor: the capacitor provides the electrical signal to start the furnace motor and can cause a buzzing sound when malfunctioning. A faulty capacitor cannot be repaired and will need to be replaced.
  • Broken blower motor: the blower motor turns the fan that circulates warm air from the furnace to the house. A failing motor can create a buzzing sound and is not able to be repaired. Given the complexity of this repair, it’s recommended that a professional service install a new blower motor. Similarly, if you find the furnace making scraping noise, it could be the fan itself that’s causing the problem. Scraping sounds indicate that a piece of the fan is broken and hitting something else. We suggest a professional assessment for this problem as well.

Furnace Making Screeching Noise

If you have a furnace making loud noise it can seem like a screeching sound is the loudest of all. Consider these possibilities when you hear a loud screeching coming from the furnace:

  • Loose or damaged blower belt: some blower fans use a belt to help turn the fan. Over time the belt can loosen or become worn out and a screeching or squealing sound results. In this case, the blower belt will need to be replaced.
  • Dry bearings or other moving parts: certain furnace parts need to stay lubricated to operate effectively. A service professional can properly lubricate any dry parts and help avoid future problems with regular maintenance.
  • Faulty blower motor: in addition to a buzzing sound, the blower motor may also make a screeching sound when failing. It cannot be repaired and will need to be professionally replaced.

A furnace making loud noise can be less startling when you know how to troubleshoot the noise and plan a repair. Dependable Heating and Air is happy to be your furnace repair service for unexpected repairs, regular maintenance or if you find your home central heater not working. Give us a call for fast and reliable service!