Is your HVAC system suddenly louder than usual? While it’s normal for your heating and cooling system to make some noise during operation, unusual sounds can be a warning sign that something’s not quite right.
At Thompson Electrical Company, we help homeowners across Bristol, Johnson City, and Kingsport stay comfortable and safe year-round. Here’s how to decode the most common HVAC noises—and what they might be telling you.
Banging or Clanking? Something Might Be Loose or Broken
Loud banging or clanking sounds could indicate a loose or broken part inside your HVAC unit—often inside the compressor. Over time, components like rods, pistons, or the blower can wear out or detach, leading to metallic banging that should never be ignored.
If you’re hearing this type of noise, shut the system down and have it inspected right away to prevent further damage.
Hissing or Whistling? Check for Air or Refrigerant Leaks
A high-pitched hissing noise is usually a sign of:
- Air leaks in your ductwork
- Refrigerant escaping from the system
- A malfunctioning valve or damaged air filter
Refrigerant leaks can be dangerous and impact your unit’s performance. If you hear hissing, it’s best to turn off the system and call a licensed technician immediately.
Pulsating or Thumping? Lines May Be Vibrating
A rhythmic pulsing noise often results from refrigerant lines making contact with walls or structural components. It may also come from a slightly imbalanced fan blade or loose panel.
Insulating refrigerant lines and tightening components can usually solve the issue—but a professional should evaluate it to ensure nothing more serious is happening.
Humming Sounds? It Could Be Electrical
A soft humming sound can indicate electrical issues, often related to the contactor relay switch. This small but critical part is responsible for signaling your outdoor unit to power on.
If the contactor is faulty, the system may hum but fail to start. This is an electrical issue that should be addressed promptly to avoid damage to your system’s circuitry.
Booming Noises? Furnace Ignition Delay
If you hear a loud boom when your furnace kicks on, there could be a delay in the gas ignition. This happens when unburned gas builds up and ignites all at once—creating a mini explosion in the combustion chamber.
This situation isn’t just noisy—it’s potentially dangerous. Shut off the furnace and have it inspected for carbon buildup and ignition system issues right away.
Buzzing Sounds? Electrical or Mechanical Trouble
Buzzing is one of the most common HVAC complaints and can be caused by:
- Loose electrical connections
- A failing condenser fan
- Frozen coils due to low refrigerant
Buzzing is often a warning sign of an electrical problem or internal wear and tear—don’t ignore it.
Rattling? Check for Loose Panels or Parts
If your HVAC system is rattling, the issue may be as simple as a loose screw or panel. But in some cases, it can also point to debris inside the system or a more serious mechanical issue.
Rattling that gets louder over time should always be looked at before it leads to more expensive repairs.
Don’t Wait—Call the Pros at Thompson Electrical Company
Strange HVAC noises are your system’s way of asking for help. If you live in Bristol, Johnson City, or Kingsport, you can count on Thompson Electrical Company to diagnose the issue and get your system back in top shape—fast.
Call us today at (423) 840-7457
We’re here to keep your home running safely and efficiently, season after season.
