Most of us are accustomed to the sounds our furnaces make. We barely notice the hum of the blower running or the little pops from the air ducts. These are normal, but what about the noises that get our attention because they aren’t what we’re used to hearing? Sounds that are suddenly loud or increasingly loud over time, or have a different quality than the typical sounds could be a signal that it is time to call a professional for a repair or maintenance. Don’t ignore them. Delaying service could result in loss of service, more expensive repairs or premature replacement.
- Loud scraping sound
A scraping, metal-on-metal sound is likely a problem with the blower wheel. One possibility is that the wheel has come loose and is scraping against the blower casing. If caught early, before there is much damage, your HVAC professional can tighten the wheel. This is a relatively easy and inexpensive fix. Another possibility is that the blower wheel is broken and needs to be replaced. Lastly, the most serious cause would be that the motor mount has broken and the entire blower assembly has dropped so that it is hitting the housing.
- Loud bang or pop when furnace starts
Dirt on the furnace burners could cause a delay in ignition. When this happens, excess gas builds up and once it does ignite there is a small explosion. Eventually, these explosions might crack the heat exchanger, which is very expensive to replace and usually results in replacing the entire furnace. If you hear this sound, have a professional check it out right away. Regular maintenance, however, will prevent this from happening.
Another cause of this type of noise could be expanding and contracting metal ductwork. This occurs when the air ducts are not the correct size or are too flimsy, if too many vents are closed or if the air filter is clogged.
- Squealing or whining noise
A high-pitched squealing noise is not as serious as the first two noises, but should be checked out by a professional to keep it from turning into a bigger problem. This type of sound may indicate a loose or damaged blower belt that should be adjusted or replaced by a technician. It could also by caused by a shaft bearing that needs lubrication; a technician can apply a lightweight oil where needed. Or, it could mean the blower motor is malfunctioning and needs to be repaired or replaced.