Some heat pump noises are normal, such as a whoosh during defrost or a click when the unit switches modes. Banging, grinding, squealing and a hum with no airflow are warnings. Turn the unit off for grinding or banging and call a licensed pro.

Climate Pros Tucson matches homeowners with licensed local pros who service heat pumps.

Why does a Tucson heat pump make noise at all?

A heat pump runs in both seasons here. It cools through long summers and heats on cold winter mornings, so its parts get a heavy workout. Tucson has about 68 days a year at or above 100F, and the airport sees fewer than 12 nights a year at or below freezing, so most of the heating duty is light.

What does each sound mean?

A whoosh or hiss during winter operation

When the outdoor coil frosts on a cold morning, the unit runs a defrost cycle. The reversing valve switches, the fan stops and you may hear a whoosh and see steam. That is normal if it lasts briefly and the unit goes back to heating. See heat pump frozen or steaming.

A click or clunk when it switches between heating and cooling

The reversing valve moves with a click or soft thump. A single sound at the switch is normal. Repeated thumping, or a valve that sticks, needs a pro. See heat pump reversing valve.

A bang at startup or shutdown

Loud banging can mean a loose part, a failing compressor mount or a duct expanding in heat. If it repeats, shut the system off and call.

Grinding, rattling or scraping at the outdoor unit

Debris in the fan, a failing fan motor bearing or loose panels are the usual causes. Desert yards carry mesquite leaves, palo verde pods and gravel that monsoon winds push into a unit. Power it off and clear loose debris only if the breaker is off. Anything that still grinds needs a pro.

A squeal at startup

A squeal can mean a worn motor bearing or a belt-driven blower slipping. Ask the pro to check the fan motor.

A hum with no airflow

A hum with no fan spin can mean a failed capacitor or a stuck motor. Turn it off and call, because a hot compressor can fail.

Hissing from the lines

Steady hissing at the refrigerant lines or coil can indicate a leak. See AC refrigerant leak signs.

Should you call now, this week or watch it?

  • Turn it off and call: grinding, banging, burning smell, hum with no fan.
  • Call soon: a squeal that continues, repeated clunks, or a noisy fan.
  • Watch it: one defrost whoosh, a single click at a mode change.

How can you lower the odds of a noisy unit?

Keep the unit clear, change filters, and schedule a tune-up before the summer and winter seasons. See heat pump maintenance and heat pump service. The Tucson HVAC hub lists areas covered.

When a heat pump sound needs a pro

Call when a sound is new, loud or getting worse. Call (520) 353-2520 and we’ll match you with a licensed local pro.