Why Is My Furnace Making a Buzzing Noise? 4 Common Causes

HVAC Logo IconBy Tom MoorDecember 1, 2023

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Woman covering her ears because of a furnace buzzing noise

Your furnace should be the source of comfort and safety, operating quietly in the background as it warms your home during the cold months. When issues suddenly develop, such as a jarring buzzing sound while the furnace operates, it can cause undue stress.

A furnace making a buzzing sound indicates something is amiss, typically a faulty component or loose ductwork. To uncover the cause of a furnace buzzing noise, it’s recommended to contact a reputable HVAC contractor who can make the appropriate repair. Keep reading as HVAC.com, your trusted source for all things HVAC, explores some of the most common causes of furnace buzzing noises.

Furnace Buzzing Noises Uncovered

1. Motor Failure

Your furnace’s blower motor performs a critical function by circulating warm, conditioned air through the ductwork and into your living spaces to keep you warm and comfortable during the cold weather season. If the blower motor malfunctions, it can create a furnace buzzing noise.

Furnace motor failure is often caused by old age, insufficient lubrication, loose parts including nuts and bolts, and a lack of maintenance. A qualified HVAC technician can inspect the motor to see whether furnace repair or replacement is the best option.

2. Bad Capacitor

bad furnace capacitor can also cause an annoying furnace buzzing sound. The capacitor’s job is to store electricity until it’s needed to start the blower’s fan motor, which distributes heated air into your HVAC system. When the capacitor ages or deteriorates, it can struggle to start the blower motor, potentially leading to buzzing or clicking noises.

3. Loose Transformer

The transformer is a crucial component of every furnace; it changes the voltage of the input power to the appropriate voltage for the furnace to use. A buzzing or loud humming noise coming from the furnace’s transformer may indicate the transformer box is loose (perhaps due to poor installation), or it’s old or malfunctioning and needs to be replaced.

4. Loose Ductwork

Sometimes a furnace making a buzzing sound isn’t actually coming from the furnace, but it is the result of loose connections within the ductwork. As conditioned air makes its way through the ductwork, it can eventually cause sections of the duct to loosen and vibrate against each other. If you notice a buzzing sound from your ductwork, contact a professional HVAC technician for ductwork sealing or repair service.

Hiring a Qualified HVAC Technician for Furnace Repair

HVAC issues can be stressful, especially if your furnace is making a buzzing noise that is disrupting your everyday life. If you observe strange noises from your HVAC system, it’s important to contact a reputable HVAC contractor as soon as possible. An HVAC technician can quickly uncover the cause of the buzzing noise and recommend the needed repair.


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