�ԹϹ���

October 23, 2020

Although winter in the Bay Area is , many homes use furnaces to stay warm when temperatures dip. If your furnace is making a loud banging noise, an unusually high-pitched sound, or other noises, it’s important to know what these sounds mean. While a lot of furnace sounds are scary, most are pretty harmless and need only general furnace repair. However, others can indicate a serious underlying issue that may need furnace replacement.

The certified HVAC techs at �ԹϹ��� have some insights into common furnace noises and what they could mean for your furnace’s performance and functionality. 

Why Your Furnace Makes a Loud Banging or Booming Sound

If you notice an unusually loud bang when your heat kicks on, it may be due to excess gas buildup. If the sound is left ignored, this annoying noise could eventually crack the heat exchanger, which is not only expensive to fix but also dangerous. If you notice a loud bang coming from your furnace, turn it off immediately and contact �ԹϹ��� for assistance.

Another common cause of loud bangs or booming sounds may be dirty burners that could delay ignition. This causes gas to build up and “explode” when the ignition finally comes on. Expanding and contracting air ducts can also cause a loud bang or boom. Schedule annual fall furnace maintenance, so our HVAC techs can inspect and clean the burners, seal and insulate the ducts (if needed), and replace the air filter. 

Identifying the Source of High-Pitched Whistling Noises

A whistling furnace can be dangerous for your household, especially if it’s caused by a carbon monoxide leak. If you’re wondering, “Why is my furnace whistling?” this high-pitched noise can come from several sources, including:

• Loose or damaged blower belts that cause high-pitched squealing or similar sounds.
• Clogged or dirty air filters create whistling noises as air pulls through them.
• Shaft bearings and other moving parts that have become dry and require lubrication.
• A malfunctioning blower motor or failed motor bearings.
• Gaps or leaks in the ductwork that cause air to escape, creating whistling noises.

What Persistent Clicking Sounds Indicate About Your Ignitor

Much like with a gas water heater, if your gas furnace is clicking but not turning on, it’s likely due to an issue with the ignitor. Here’s what persistent clicking sounds could indicate about this important component:

• The ignitor may be cracked or broken and can’t light the gas to turn your furnace on.
• A dirty flame sensor can fail to cause ignition, but the furnace keeps trying, which creates the persistent clicking noises.
• If the gas valve is blocked, the ignitor will continue clicking, even though the gas can’t reach the burner.

The Dangers of Metal-on-Metal Scraping Noises

Scraping is a common furnace blower motor-related noise, and some loud metal-on-metal furnace scraping sounds can be dangerous. If you hear this noise, turn your furnace off immediately and rely on �ԹϹ��� for repair to prevent further damage to your equipment.

Here’s what homeowners should know about unpleasant furnace scraping noises:

• The blower fan may have come loose and is now hitting the blower housing.
• The blower fan itself could be broken and may require professional replacement.
• The piece holding the motor and blower assembly is broken and loose, hitting the housing and creating a loud scraping sound.

Understanding Why Your Air Ducts Pop and Bang

Several things may cause HVAC ductwork to make popping and banging sounds:

• When warm air fills the ducts and then contracts when the heater stops running, it creates thermal expansion that can cause popping sounds.
• Sudden pressure changes when the blower fan turns on can push the air ducts and lead to a popping noise.
• A clogged air filter limits airflow, creating negative pressure in the return ducts that creates banging noises.
• Improperly sized or poorly designed air ducts can cause the metal to flex and shake.

Causes of a Loud Humming or Buzzing Internal Component

A loud buzzing or humming noise coming from the furnace might be due to the following factors:

• A faulty capacitor or transformer may struggle with voltage, creating buzzing sounds.
• A dirty air filter forces the blower motor to work harder, causing loud humming noises.
• Worn-out bearings or a dying blower motor will often produce a humming or buzzing noise.
• Vibrations from loose screws, air ducts, or access panels can create constant furnace rattling sounds.
• Electrical issues, such as loose wiring or problems with relays or the control board, are common causes of buzzing sounds from a furnace.

Why a Squealing Sound Might Mean a Failing Blower Belt

A failing blower belt is one of the most common causes of a furnace squealing noise. This occurs when the belt becomes worn, brittle, or loose, causing it to slip against the pulleys and produce an unpleasant squealing sound. When the belt slips, it generates heat and friction, producing high-pitched screeching noises. A loose or failing blower belt should be adjusted for tension or replaced if needed.

Differentiating Between Normal Operation and Emergency Noises

If you’re wondering why your furnace pops when it turns on, or why it's making a weird screeching sound, you’re not alone. Ignoring any unusual furnace sounds may lead to major equipment failure over time. It’s important to understand the difference between sounds that indicate normal operation and those that indicate an emergency.

Normal operation

Soft humming noises are typically harmless and usually caused by the blower motor running in the background. Clicking at startup or shutdown is also normal and usually means the thermostat is signaling your ignition system. Whooshing noises are often caused by air circulating through the ducts.

Emergency noises

Loud bangs and booms are an emergency and can be caused by delayed ignition due to gas buildup, which can damage the heat exchanger. Extreme screeching or squealing is often due to a worn-out blower motor or a slipping belt, while grinding or thumping sounds are usually from a broken blower wheel or motor failure. Constant, rapid clicking may be caused by a faulty flame sensor or circuit board and requires professional attention. 

How Loose Panels Contribute To Rattling and Vibrations

A rattling or furnace vibration noise can be a sign of a loose panel or loose screws. When the access panel isn’t secured tightly, it will vibrate against the furnace frame. Loose panels can also create gaps that lead to air leaks, reducing your furnace's overall efficiency and forcing it to work harder. Over time, the ongoing friction from the vibration caused by loose panels weakens the screw holes and mounting points, making the rattling sound louder and more intense.

Contact �ԹϹ��� for a Professional Furnace Diagnosis

Choose �ԹϹ��� for heating, cooling, plumbing, electrical, insulation, and ductwork across the Sacramento area, South Bay, Concord, and the East Bay.

Contact �ԹϹ��� �ٴǻ岹��!��