My Lennox Furnace Makes a Buzzing Sound While the Heat Is on

Compressor

• The compressor, which is located in the middle of the condenser, can make a buzzing sound when the furnace is working. This is a normal sound and is not cause for concern. Order a noise-suppression blanket from Lennox to reduce the noise.

Contacts

• Disconnect power to the Lennox furnace and allow the furnace to cool completely, and then open the front access panel. Turn the household thermostat to “A/C” and wait for the air conditioning to turn on. If the buzzing sound begins, the contacts inside the furnace are to blame. Cleaning the contacts with a clean, dry cloth can prevent the contactor from completely engaging when the furnace is running, which creates a buzzing sound. Clean other excess dirt and debris around the burner while cleaning the contacts. Close the access panel.

Loose Parts

• During installation or over time, the hardware on the Lennox furnace may become loose, which creates a vibrating and buzzing sound when the furnace is working. Open the access panel and listen carefully for the buzzing sound. Tighten the hardware in the area where the noise is loudest.

Blower Compartment

• Sometimes the blower becomes dirty and creates a humming sound. Open the blower compartment, which will cause a switch to automatically shut off power. Depress the switch, allow the furnace to start back up, and listen for the buzzing sound. Tighten the mounting at the location where the sound is loudest.