Not every sound from a heat pump signals a problem — some are completely normal parts of how the system operates. Others are early warnings that something needs attention before it becomes a larger repair. Understanding which is which helps you decide when to wait and when to call a technician.
Heat pumps make noise during normal operation — clicking at startup and shutdown, gentle humming from the compressor, the sound of the outdoor fan, and whooshing or gurgling sounds during defrost cycles. These are expected and do not indicate a fault.
Sounds that appear suddenly, grow louder over time, or are clearly different from the system's usual operation are worth paying attention to. Banging, grinding, screeching, continuous hissing, or rapid-fire clicking that won't stop are not normal sounds and usually indicate a component that needs inspection or repair.
When in doubt, note when the sound occurs, how long it lasts, and whether it is coming from the indoor air handler or the outdoor unit — this helps a technician diagnose the issue faster.
These sounds are part of how a heat pump operates. You do not need to call a technician if you hear these.
A click or two when the heat pump starts or stops is normal. This is the relay or contactor — an electrical switch — engaging or disengaging to control the compressor and fans. It is a brief, distinct click, not a repeating or prolonged sound.
A gentle whooshing sound as the system starts up or during operation is refrigerant moving through the system. This is normal refrigerant flow and is not a sign of a leak or problem. It typically lasts only a few seconds and then fades as the system reaches steady operation.
The compressor produces a steady low hum during operation. The outdoor fan also makes a consistent hum or whoosh as it spins. Both are normal sounds of the system running. The hum should be consistent — it is the change in pitch, volume, or character that would indicate an issue.
During cold weather, heat pumps periodically enter a defrost cycle to clear ice from the outdoor coil. This involves reversing the refrigerant flow, which can produce a hissing or gurgling sound, sometimes accompanied by a rush of steam from the outdoor unit. This is completely normal and lasts only a few minutes. The system will resume normal operation on its own.
These sounds are not normal parts of heat pump operation. If you hear any of them, read the guidance below — some require shutting the system off and calling a technician promptly.
A loud banging or clanking sound — especially one that is sudden or rhythmic — usually means something is loose or broken inside the unit. A fan blade, loose mounting hardware, or a failing compressor component can all produce this sound. Turn the system off and call a technician. Continuing to run the unit can cause further damage.
A grinding or high-pitched screeching sound almost always points to a motor bearing issue — either in the indoor blower motor or the outdoor fan motor. Bearings wear over time; when they fail, the metal-on-metal contact produces this noise. This is a situation to shut the system off immediately and call a technician. Running the system further risks motor failure and a more expensive repair.
A rattling sound can come from debris — leaves, twigs, or small objects — that have gotten inside the outdoor unit and are contacting the fan. It can also indicate loose panels, screws, or covers on either the indoor or outdoor unit. If debris is visibly accessible and can be safely removed without opening the unit, that may resolve it. If the rattling persists or the source is unclear, have a technician inspect it.
A brief hissing sound during a defrost cycle is normal, as noted above. A continuous hissing — one that occurs outside of defrost cycles, lasts an extended time, or is noticeably louder than usual — may indicate a refrigerant issue. Call a licensed technician for diagnosis. Do not attempt to add refrigerant yourself: refrigerant work is regulated, requires certification, and incorrectly adding refrigerant can damage the system and create safety hazards.
A single click at startup is normal. Rapid or repeated clicking that continues after the system should have started — or clicking that repeats every few seconds — is not. This typically points to a control board fault, a failing capacitor, or an issue with the contactor. These are electrical components that require a licensed technician to diagnose and replace safely.
A few things homeowners should avoid when dealing with unusual heat pump sounds.
These sounds often indicate a mechanical failure in progress. Running the system while a component is broken or failing can turn a repair into a replacement. If you hear a sudden banging, clanking, or grinding noise, shut the system off and contact a technician before operating it again.
If you suspect a refrigerant issue based on continuous hissing or reduced performance, do not attempt to add refrigerant. Refrigerant handling requires certification under Canadian regulations. Adding refrigerant without a proper diagnosis can mask a leak, overcharge the system, and create safety risks. Only a licensed HVAC technician should handle refrigerant.
The electrical components inside both the indoor air handler and the outdoor unit — including capacitors — can store dangerous amounts of electrical energy even after the system is powered off. Do not open electrical panels, disconnect boxes, or access covers on the unit. Capacitors can discharge without warning and cause serious injury. Leave all internal inspection to a licensed technician.
New, loud or persistent mechanical or electrical noise should be professionally diagnosed before it becomes a larger repair.
Answers to the questions we hear most often about heat pump sounds and what they mean.
Our licensed technicians diagnose and repair heat pumps across Metro Vancouver. Whether your system is banging, screeching, clicking, or making a sound you haven't heard before, we can identify the cause and advise on the right repair.
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