5 Reasons Why Your Furnace is Making a Low Humming Noise when Off

A quiet furnace is a sign of a well-functioning heating system. However, if you notice a low humming noise coming from your furnace when it’s turned off, it could indicate a potential problem.

In this article, we’ll explore five reasons why your furnace may be making this sound and offer solutions to remedy these issues.

5 Reasons Why Your Furnace is Making a Low Humming Noise when Off

Blower Motor

A faulty blower motor can cause humming noises. This might be due to worn-out bearings or loose parts. To fix this, it’s best to call a professional HVAC technician for inspection and possible replacement.


Sometimes, the ductwork can produce noise due to thermal expansion and contraction or if they are not properly installed. Ensuring that your ductwork is properly sealed and insulated can help eliminate these noises.


The transformer in your furnace may also be the culprit of the humming noise. It might be due to a loose lamination or mounting hardware. In this case, the transformer might need to be replaced.


A humming noise might be caused by the fan in the furnace. If the fan blades are damaged or if the motor is faulty, they could create a humming noise.

A professional can inspect the fan and determine if a repair or replacement is needed.

Electrical issues

Loose electrical connections or failing capacitors in the furnace can also cause humming noises. These electrical issues should be addressed by a professional to ensure safe and proper repairs.

What to Do if the Blower Motor is Bad?

If the blower motor in your furnace is bad, it may produce a humming noise. This often requires a professional to fix. They will inspect the motor, identify the problem, and then decide whether a repair or replacement is necessary.

What to Do if the Ductwork is Bad?

Bad ductwork can lead to a humming noise when your furnace is off. To address this issue, it may be necessary to have an HVAC professional inspect your ductwork, fix any leaks, and ensure it is properly sealed and insulated.

What to Do if the Transformer is Bad?

If the transformer in your furnace is bad, you’ll likely hear a humming or buzzing noise. The transformer will likely need to be replaced by a professional HVAC technician.

Can My Furnace Make Noises When Off?

Yes, your furnace can make noises even when it’s turned off. This might be due to several factors such as a bad blower motor, problems with the ductwork, a faulty transformer, a damaged fan, or electrical issues.

Is a Buzzing Furnace Dangerous?

A buzzing furnace can potentially be dangerous, as it could indicate a serious problem like a gas leak or electrical issue. It’s crucial to contact a professional immediately to investigate and rectify any problems.

What to do if Furnace Transformer is Buzzing When Off?

If your furnace transformer is buzzing when off, it likely needs to be replaced. This should be handled by a professional HVAC technician to ensure safety and accuracy.


A humming noise from your furnace when it’s off shouldn’t be ignored. As we’ve discussed, this sound can indicate a variety of problems, from a bad blower motor to faulty ductwork.

Don’t hesitate to reach out to a professional HVAC technician to ensure your furnace is safe and functioning correctly.

Regular maintenance can also go a long way in preventing these issues from occurring. By taking proactive steps, you can ensure your home stays warm and comfortable, and your furnace stays quiet and efficient.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

Related Posts