Your HVAC system is supposed to keep your home comfortable—not make you feel like you’re living next to a construction site. If you’ve noticed strange noises coming from your furnace or air conditioner, you’re not alone. While some sounds are perfectly normal, others could be a sign that something’s wrong.

A rattling, banging, or high-pitched squeal could mean there are loose parts, airflow problems, or even electrical issues. Ignoring these sounds might lead to bigger (and more expensive) problems down the road.

So, what’s causing the noise, and should you be worried? In this guide, we’ll break down the most common HVAC sounds, what they mean, and when it’s time to call MTN Valley Heating & Air Conditioning for expert help in Northern Utah.

1. Banging or Clanking

A loud banging or clanking sound coming from your HVAC system is never a good sign. It often points to something loose or broken inside the unit. If you hear this noise when the system kicks on or off, it’s worth investigating before the problem worsens.

Possible Causes:

• A loose or broken blower fan
• A misaligned or unbalanced motor
• A cracked heat exchanger (a serious issue in furnaces)

If the sound is coming from inside the furnace or air conditioner, it’s best to turn off the system and call a professional. Continuing to run it could cause further damage and lead to costly repairs.

2. Hissing or Whistling

A hissing or whistling noise can mean air is escaping from somewhere it shouldn’t be. While some air movement sounds are normal, a loud or persistent hiss could be a sign of a bigger issue.

Possible Causes:

• Air escaping from leaks in the ductwork
• A clogged air filter restricting airflow
• A refrigerant leak, which can affect cooling performance

If the sound is coming from the vents, checking and replacing the air filter may help. If it seems to be coming from the indoor or outdoor unit, there may be a refrigerant leak, which should only be handled by a professional.

3. Rattling or Vibrating

A rattling noise often means something inside the system is loose and shaking around while the HVAC runs. While it might start as a minor annoyance, leaving it unchecked can lead to bigger issues down the road.

Possible Causes:

• Loose screws, panels, or fasteners
• A failing blower motor
• Debris caught in the outdoor unit

If the noise is mild, you can try tightening any loose screws or panels. If it persists, or if the rattling turns into loud vibrations, it’s a good idea to have a technician take a look.

4. Squealing or Screeching

A high-pitched squealing or screeching noise coming from your HVAC system is hard to ignore—and for good reason. This type of sound usually means there’s a mechanical issue with a moving part inside the system. If left unchecked, it can lead to more significant damage and even system failure.

Possible Causes:

• A worn-out or misaligned blower belt
• Motor bearings that need lubrication
• A failing compressor

If the noise starts suddenly, it’s best to shut off the system and schedule a repair. A worn belt or dry bearings can sometimes be fixed with minor adjustments, but if the compressor is involved, it may require a more in-depth repair.

5. Clicking Sounds

Hearing a single click when your HVAC system starts up is normal. But if the clicking continues throughout the cycle or happens repeatedly without the system turning on, it could indicate an electrical problem.

Possible Causes:

• A failing relay switch
• Electrical issues in the control board or thermostat
• A cracked heat exchanger (a serious problem in furnaces)

Since electrical problems can lead to bigger safety concerns, it’s best to have a technician inspect the system sooner rather than later. A cracked heat exchanger, in particular, can pose a carbon monoxide risk and should be addressed immediately.

6. Buzzing or Humming

A low humming sound from your HVAC system is normal, but a loud buzzing or excessive vibration can be a red flag. Electrical components inside the system may be malfunctioning, which can cause damage if not addressed quickly.

Possible Causes:

• A failing capacitor or relay switch
• Loose wiring inside the unit
• A malfunctioning compressor

If your HVAC system is buzzing but still running, it’s a good idea to turn it off and call for an inspection. Electrical issues can worsen over time and may eventually cause the system to stop working altogether.

7. When to Call a Professional for HVAC Noises

Some HVAC noises can be fixed with simple maintenance, like changing a filter or tightening a loose panel. But in many cases, strange sounds are an early warning sign of a bigger problem. Ignoring them could lead to higher repair costs, reduced system efficiency, or even a complete breakdown.

Signs You Should Call a Professional:

• The noise is getting louder or happening more frequently
• The system is running, but heating or cooling performance has dropped
• You hear electrical buzzing, clicking, or hissing from the unit
• A banging or clanking sound happens every time the system cycles on or off
• You suspect a refrigerant leak or a cracked heat exchanger

If you’re unsure whether a noise is normal or not, it’s always best to have a technician check it out. Catching problems early can prevent expensive repairs and extend the life of your HVAC system.

Contact MTN Valley Heating & Air Conditioning 

Strange noises coming from your HVAC system aren’t just annoying—they’re often a warning that something isn’t working properly. From loose components and clogged filters to electrical problems and failing parts, identifying the cause of the noise early can save you time, money, and stress.

If your heating or cooling system is making unusual sounds, don’t wait until the problem gets worse. MTN Valley Heating & Air Conditioning provides expert HVAC diagnostics and repairs in Northern Utah. Whether it’s a minor issue or something more serious, our team is here to help keep your system running smoothly.