Noises Your Furnace Should Not Be Making -Dowd HVAC - Heating and Air Conditioning

Noises Your Furnace Should Not Be Making

Your furnace will make a sound here or there during operation. For example, you may hear a sound when your furnace first turns on for a heating cycle or a humming or blowing sound as airflow moves through the system. But all of the sounds should be fairly gentle and quiet.

Any sounds that are particularly alarming or out of the ordinary are a sign that it’s time to schedule a heating service in Hatboro, PA. You can keep reading to learn more about some of the most common sounds that we get calls about and what each one of them means for your furnace.

Banging or Booming

A loud banging sound inside of any heater can indicate that something large is loose inside of the system. Instead of a gentle rattle, smaller components might make when they are loose, larger items bang around. A booming sound is particularly concerning when you have a gas furnace. Sometimes the igniter malfunctions and does not light right away.

If this happens, gas may continue to build up in the chamber until there is more than necessary by the time ignition happens. When the flame finally lights, a small explosion happens and results in a booming sound. This can put a lot of strain on the heat exchanger and even lead to cracks that allow carbon monoxide to leak into your home.


When the pressure from explosions during combustion cracks your heat exchanger, you may then hear a rattling sound afterward. The loose pieces of metal that came apart may vibrate during operation and result in a rattling sound. The rattling could be loud or soft.

Of course, rattling can also be attributed to the ductwork if you have a central heater. It is normal to hear a little rattling here or there from your ductwork since it is made of thin sheet metal. But if you hear loud or persistent rattling coming from your ductwork, it means that some of the pieces are loose and need to be secured.


Fan belts often squeal when they come loose. Fan belts need to be tight and secure for proper operation. But over time fan belts can loosen up around the attached components and need to be replaced. When you hear a squealing sound, it’s important to turn your heater off and get it checked out. Allowing the sound to continue could lead to a belt that snaps off and does more damage inside of the system.


Screeching is another sound that should be concerning. It often happens if lubrication dries up between components and leads to the metal pieces grinding together. Instead of effortless operation, you wind up with a more clunky and loud operation. If parts grind together for too long without lubrication they will need to be replaced completely.

Contact Dowd Mechanical Heating & Air Conditioning to schedule an appointment for heater service. A Degree Above the Rest.

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