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Furnace Noise: Know What Problems To Look For

It’s the stuff of horror movies: a loud, banging noise echoes through the dark, quiet house, waking you from your pleasant dreams. You put on your robe, walk down the hall, and as you creep down the stairs, your hand hits the light switch, only to find that the source of the racket is….your furnace.

A noisy furnace can be bothersome, especially if the banging, whistling, or thumping is particularly loud. Unless you’re a licensed technician, these sounds may concern you and leave you wondering if your furnace needs to be repaired or replaced. While some noises are normal, a functioning furnace shouldn’t make too much sound. If you notice your furnace making loud, strange noises, make sure you know what to do and who to call.

In order to determine why your furnace is so noisy, consider the following:

1. Does it make a loud banging noise when you turn the furnace on?

If the noise only occurs right when your furnace comes on, you might be dealing with a starting issue. This problem, called a delayed ignition, can make a very loud noise right as you start your furnace because it ultimately causes buildup where the furnace ignites, making it start with a bang—literally. This can be extremely dangerous, which is why you should call a trained professional immediately. In the meantime, turn off your furnace, or shut off the gas to the furnace.

2. Is the furnace noise a whistling, or high-pitched screeching?

When a furnace whistles or screeches, it could indicate any number of mechanical problems. The moving parts could have become dry or damaged, or the blower motors might be working incorrectly. On the other hand, a damaged belt can cause a squealing noise, as can gaps between the furnace duct and blower. If you hear a whistling noise, you could start by trying to change the filter. If the issue has to do with the blower motors, you could try replacing the worn-out belt, or lubricating the parts of the motor that are making noise. Sometimes, the noise is simply a matter of too much friction.

3. Are the noises loud “bangs” or similar to gunshots?

Loud banging noises are perhaps the most common issues associated with furnaces, but that doesn’t make them any less dangerous. As we explained above, a loud bang when you first turn on your furnace could indicate an ignition issue, but if the noise persists, it could have more to do with a duct issue. These noises could also be the result of dirty burners or oil canning problems.

In order to address this type of problem, try replacing the dirty filter or check the burners to see if they need to be cleaned. If it is an oil-canning problem, you should get professional help because it is very likely your duct work will require additional support or repairs.  

4. Rattling and rumbling noises plaguing your furnace?

If you notice that your furnace is rattling, rumbling, or vibrating it could be a simple matter of a loose device or component. For example, your furnace may have a few loose screws, loose ducts, loose panels, or it might mean the mechanisms are dirty and need a good cleaning. Or, a rattling noise might indicate a leak in your heat exchanger, which could cause the system to overheat or cause the safety switches to engage.

To fix any loose, rattling equipment, you could look inside the furnace and tighten any loose screws you come across. If you find a loose panel or something else rattling, you could try securing it with duct tape until you can seek professional help.

5. Do you hear metal scraping on metal?

When you hear a scraping noise that sounds as if metal is grinding against metal, your furnace’s blower wheel might be malfunctioning. This sound might also indicate a motor issue, which might also lessen the effectiveness of your heater.

If you find yourself dealing with a noisy heater, it’s always better to be safe rather than sorry. Some noises might indicate a simple maintenance issue, while others could point to larger, potentially dangerous problems. In any case, our experienced professionals are here to help with your furnace repair, replacement, or installation.

 Contact Crisafulli Bros. Plumbing & Heating Contractors, Inc. to speak with our Albany HVAC technicians about your next service!

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