In the winter, you may look forward to the gentle hum of your furnace kicking on. That’s the kind of furnace noise that you like. Not all furnace sounds are so pleasant. Pops, squeaks, grunts, whistles and squeals suggest that there may be something wrong with your system.

When you hear things like that, you might immediately start to wonder what’s wrong. Your best bet is to call a professional for furnace diagnosis and repair. Keep reading to learn more about furnace sounds.

1. Air Filter

Strange furnace sounds could be caused by something as simple as a dirty air filter. When the filter becomes clogged with old dust and debris, air doesn’t travel through it as effectively. The furnace may have a hard time pulling in enough air, or the blower will have to work harder to get warm air where it needs to go. Issues like that can cause your system to start making unusual noises, such as a whistling sound.

2. Air Vents

Dirty vents can cause the same trouble as a filter that needs replacing. As the system tries to force warmed air through a blocked vent, it may start to make a high-pitched whistle. Opening the vents or cleaning them could fix the problem. Another solution might be to move large objects that are sitting in front of the vents.

3. Ductwork

A rather loud pop may happen soon after the furnace kicks on each time. This sound is also described as a bang. That’s a normal occurrence. It’s just a sign that your ductwork is cold, which causes it to contract. When the warm air hits it, the metal expands. The rapid expansion causes a popping sound.

If this is only happening now and then, it’s probably no big deal. In homes where this is a particularly loud or repetitive problem, though, it might be a good idea to do something about it. Sometimes the fix is as simple as cleaning the ductwork or switching the filter. In other cases, the best solution might be to replace the ducts with larger ones that are more appropriate for the size of the house.

4. Belts

Sometimes, a heating system starts to squeal and screech while it’s running. Those noises often indicate a belt problem. Belt issues can be fairly easy repairs when caught early. The belt may need to be tightened or replaced. Unfortunately, ignoring a problematic belt for a while could lead to bigger repairs. It’s best to address the squeaky belt before it snaps. Besides, won’t it be more pleasant in your house once that shrieking sound is gone?

5. Ball Bearings

Inside the blower motor are ball bearings. Over time, they can get loud. You might hear scrapes or squeals from your system. Typically, the sound isn’t too high-pitched. Rather, it can be described as a dry squeal. Fixes for this problem could involve lubricating or replacing the bearings.

6. Blower Fan Motor

Your motor of the blower fan has more parts than just the motor bearings. Other components can become noisy as well. The culprit could be one of the electrical pieces that make the motor run, such as the transformer or the capacitor. Or, the entire motor may need replacement.

Often — but not always — loud blower fans are only noisy for part of the cycle. They make a lot of noise at the beginning of each heating cycle, but then they quiet down. That’s because a large amount of work goes into getting the fan spinning. Once it’s moving, the parts don’t have to strain so hard, and they become quieter. Since the noise is only intermittent, you might assume that this problem isn’t too severe. That’s not always the case. If your furnace is buzzing or making a loud hum every time the heat kicks on, then a motor repair or replacement may be in your future.

7. Ignition System

In a gas furnace, an ignition system lights the gas at the beginning of each cycle. A problem with the igniters or the burners could be the cause of your strange furnace noises. Multiple things could go wrong in this area. A valve or another part may stop working, which means that gas isn’t released when it should be — or there isn’t enough of it. The igniters try to do their job, but there’s nothing to light.

The air-to-gas ratio might be thrown off. Whether there’s too much air or too much gas, it’s not a good thing and can upset the ignition process. The igniter might not click on properly when it’s supposed to. That can cause a small buildup of gas inside the system. Once that bigger-than-normal batch of gas ignites, you’ll hear it!

Perhaps the burners themselves are dirty. They could also be misaligned. In situations where the igniters are trying to work, but there’s not enough gas there to make it happen, clicks are the most common sound. When the ignition doesn’t happen at the right time, so there’s a gas buildup, you may notice banging sounds coming from your system.

These situations definitely call for prompt attention. For one thing, they mean that your furnace isn’t doing its job correctly. Also, chronic ignition delays may cause cracks in the heat exchanger — a dangerous and costly problem.

8. Heat Exchanger

The part of your furnace where the cool air becomes warm is called the heat exchanger. Unfortunately, this piece has the potential to crack. If it does, you might notice a troubling sound coming from your furnace. Rattling noises are the most common sound associated with cracked heat exchangers. The sound is caused by an expansion in the heat exchanger’s coils. It’s often loudest right at the beginning of the heating cycle.

This is a serious problem. Cracks in a heat exchanger can allow poisonous carbon monoxide to escape into the home. Carbon monoxide poisoning can cause illness or even death. The gravity of the situation should serve as a powerful reminder to always have unusual furnace noises checked by a heating professional.

9. Loose Components

If one component of your furnace gets out of place, it can get in the way of other parts or interfere with how the system operates. That can cause all sorts of noisy trouble. You might hear clacks, thwaps, rattles or other sounds. This issue isn’t limited to any one part, so it’s best to have a professional inspect the system and identify where the noise is coming from. The problem could be a door or a panel, or it could be something on the inside of your system.

The next time you need furnace assistance, reach out to Fusion Plumbing & Air in Tuscon. You can also depend on Fusion Plumbing & Air for cooling, plumbing, drain and sewer help. We can install, repair and maintain your important home systems. We also provide commercial HVAC services. Give Fusion Plumbing & Air a call today to learn more about our services.

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