How to Troubleshoot a Rattle in a Furnace


Your home furnace is responsible for maintaining a comfortable interior temperature during colder months. As with any home appliance, a furnace may encounter various problems throughout its life. If you hear a “rattle” coming from the furnace, you may troubleshoot this appliance to help locate the cause of this sound.

Things You'll Need

  • Phillips-head screwdriver
  • Damp cloth
  • Compressed air can

Blower Fan Belt

  • Turn off power to the furnace by locating the circuit breaker designated for this appliance. Flip the breaker to the “Off” position.

  • Remove the furnace front panel. The exact steps necessary to remove the front panel may vary according to your specific furnace model. Typically, the panel may be removed by unscrewing the screws with a Phillips-head screwdriver. Carefully place the front panel to the side.

  • Locate the blower fan belt. The location of the belt may vary; however, it is a circular belt attached to the blower, which is a small box. Inspect the belt for cracking, fraying or glazing. If the belt is damaged, replace. Push down on the center of the belt. It should feel taut and only move ½ inch to ¾ inch. If the belt is loose, tighten by locating the attachment bracket and loosening the bracket. The bracket is typically located near the blower motor.

  • Manually move the motor assembly gears until the belt is at the ideal tightness. Hold the gears in place and tighten the attachment bracket. Do not tighten the belt too much as this can damage the fan and motor bearings. Tighten until the belt has ½ inch give when pushed down.

  • Replace the front panel, and turn the circuit breaker to the “On” position. Activate the furnace by turning up the temperature. Listen to see if the rattle has disappeared, if not, move onto the next section.

Dirty Burners

  • Turn off electricity to the furnace by flipping the circuit breaker assigned to the furnace to the “Off” position. Disconnect gas flow to the furnace, if it’s a gas furnace, by flipping the gas valve to the “Off” position.

  • Access the furnace burners by removing the front panel. Removing the panel may be done by unscrewing the attachment screws with a Phillips-head screwdriver; however, the exact removal steps may vary according to your furnace.

  • Locate the burners, which are typically found near the blower box. Clean around the burners with a damp cloth. Remove dust and look for rust flakes typically located around the base of the burners. Wipe the entire burner area to remove debris. Dirty burners typically cause a “rattling” sound.

  • Unscrew the burners from their housing. Gently clean each burner with a wire brush. Pay close attention to the opening of the burners as rust and dust tend to accumulate to this area.

  • Spray the inside and outside of each burner with compressed air. Carefully screw the burners back into their housing.

  • Return power and gas to the furnace by flipping the circuit breaker to the “On” position and the gas flow valve to the “On” position. Activate the furnace by turning up the temperature on the thermostat. Contact a professional repairman if the “rattling” noise has not disappeared.

Tips & Warnings

  • Clear items away from return-air vents and grilles as obstructing these vents reduces airflow to and from the furnace, which may result in a humming or rattling noise.
  • Do not attempt to clean the furnace if you are unsure of how to turn off electricity or gas flow.

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