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Why is my furnace making noises?

Posted on: February 8, 2016

If your furnace is making noises, you should address the issue before the problem gets worse. The only problem is furnace noises may be tricky to diagnose on your own. For safety reasons, never try to fix a furnace unless you have training and experience. Instead, call an HVAC professional to inspect the equipment if you hear your furnace making any of the following noises.

Give us a call at 240-399-5051 or fill out the contact form on this page to schedule an appointment for furnace repair!

Popping or booming in the ductwork

When ducts expand as hot air travels through them, they may make a popping or booming sound. If possible, find the place where the sounds are coming from. The area can then be tightened by attaching a metal brace. If you can’t locate the spot, or the furnace noise seems to come from everywhere, a technician may be able to replace the ductwork with flexible hoses instead.

Booming in the furnace when it ignites

If you hear this noise, the burners—which are pipes located under the flame with a wide opening at one end—have most likely accumulated carbon and ashy debris. The gas builds up behind this until it finally pushes through, making a booming noise when the gas ignites. Sometimes the burners light in succession and you hear boom, boom, boom. To prevent damaging your furnace, don’t delay fixing this problem.

Clicking before the gas reignites

The flame sensor telling the furnace when the gas is lit probably has build-up on it. This wire or rod sticks up into the center of the flame. You can turn off the furnace and clean the sensor with sandpaper. If cleaning it doesn’t seem to work, you may need to replace the sensor.


This noise most likely indicates a problem with the blower motor or shaft bearings. A belt in the blower motor may be slipping, which requires immediate attention to prevent the belt from failing altogether. A technician can replace the damaged belt to fix the problem and stop the noise. Squealing could also mean the shaft bearings need oil. Hire an HVAC contractor to apply light weight oil to the lubrication ports as needed.

Rumbling when the burners are off

If a low-pitched rumble occurs when the burners are off, it probably means the pilot light is adjusted poorly. A technician knows the proper way to adjust the pilot light and end the rumbling furnace noise.

Rumbling when the burners are on

When rumbling occurs while the burners are on, the gas burners might be dirty. This occurs over time as debris from the furnace collects on the burners. A technician can perform maintenance in this area to stop the noise and help your furnace run more efficiently.

Scraping sounds

Most likely, the motor bearings are wearing out. Shut off your furnace immediately if you hear these scraping noises and call for service to prevent additional damage from occurring.

Vibrating or rocking sounds

If the furnace sounds like it’s rocking around or vibrating, either the blower motor or wheel is probably off balance. With a visit from a qualified technician, the unbalanced components of your furnace can be adjusted to increase efficiency and stop the noise.

All of these furnace noises require immediate attention to prevent damaging your system and resulting in an expensive repair. To speak with a qualified professional about the furnace noises you’re hearing, please contact James A. Wheat & Sons today.