furnace making noise when off

Most mechanical devices make some noise whenever they are operating. Furnaces aren’t an exception, but a properly functioning furnace should not make too much noise. If your furnace is making an unusually loud noise, there is perhaps something wrong with it, and may need repair. We don’t recommend attempting DIY repair instead call a professional for furnace service. What causes the furnace’s noise-making mainly depends on the type of noise that you’re hearing. That said, here are some common furnace sounds and the most likely reasons for them.

Scraping Noises

This noise is typically caused by either a broken blower wheel, a loose blower wheel, or a broken motor mount. This noise can be alarming since it resonances like metals rubbing against each other. Several reasons make the blower wheel makes a scraping sound. First, it could be broken and may require replacement. It can also be loose and make a scraping noise because of pounding against casing of the blower. If you hear some scraping noise, it is important to call a technician to inspect it. This is because scraping sound can lead to serious issues including wear and tear on your system if unresolved.


A furnace that has a thumping sound indicates that your blower motor or wheel is unbalanced. It is a kind of sound similar to a washing machine. Although this sound is not as distracting or alarming as many of the sounds already mentioned, it is important to get fixed by a professional immediately.


If the furnace is still working correctly, the humming sound could be a result of a loud transformer. Nevertheless, persistent problems complemented by humming indicate that there is an issue with the interior capacitor or fan. Moreover, if your furnace is producing a loud buzzing or humming sound, there could be an issue with the motor. Contact a furnace contractor to come and inspect the electrical components if it makes a buzzing or humming sound throughout their operation.


This sound commonly means that your blower belt is not well lubricated or the fan belt could be loose. Moreover, the blower motor has bearings and it is prone to drying over time. It also indicates that you have a malfunctioning blower motor, failing compressor, and belt that needs replaced or unmaintained furnace bearings. This problem can be easily solved by adding lubricant. Moreover, you also need to contact a professional to assist with belt replacement and this will prevent the furnace from malfunctioning.

Banging and Popping Noises

Popping and banging noises are normal. Often, furnaces can make these sounds as the ducts contract and expand. Loud bangs can mean several things such as bent sheet metal siding, clogged filters, closed vents, and an undersized duct. If your furnace starts making loud popping and banging noises, pay attention to the problem. This is because it can crack the heat exchanger and could lead to a costly repair.

If you notice any of these sounds disrupting your home peace, it is essential to contact a trusted HVAC professional to repair your furnace. To learn more, contact our furnace repair and installation team today.