Diagnosing Heat Pump NoisesIt’s normal to hear some noise when your heat pump starts up and shuts down, and while it’s operating. These low-key sounds can include humming, clicking, whooshing and squeaking. If a loud noise develops, it’s important to get the cause diagnosed, because it can be a sign of serious problems within your HVAC system.

Here are some sounds that deserve further investigation, and their possible causes:

Metal-on-Metal Banging

A loud metallic banging noise from inside your heat pump cabinet is most likely due to a loose fan blade that’s striking nearby components. To minimize potential damage, it’s best to shut your system off and call for professional help.


Vibrations within your HVAC system while it’s operating can cause an annoying rattling from loose hardware, ductwork, piping or other components. Tightening any loose cabinet screws may be all that’s necessary to stop the racket, but if not, an experienced technician should check for other culprits.

Gurgling and/or Hissing

Gurgling noises from your HVAC unit can be a warning of a low refrigerant level. If you hear hissing, there may be a refrigerant leak. Both of these noises need prompt attention, because running your system without sufficient refrigerant not only wastes energy, it can ruin the equipment.


Heat pumps often make a humming noise when in defrost mode, and this is normal. However, if your unit starts buzzing loudly, but doesn’t cycle on, you need to have it assessed for electrical problems such as a failed capacitor, stuck relay switch, or faulty motor.

Shrill Shrieking

High-pitched shrieking from a heat pump can indicate a serious issue with the compressor, and/or dangerously high refrigerant pressure. Bad motor bearings and a misaligned/frayed blower belt can cause similar noises, so it’s important to get an expert diagnosis.


Grinding noise can be caused by insufficient lubrication or excess dirt buildup on motors and other moving parts. To ensure your HVAC components stay running quietly and reliably, schedule regular maintenance so they’re always clean, tuned-up and properly lubricated.

For help diagnosing heat pump noises in your Dayton home, contact us at Detmer and Sons.

Our goal is to help educate our customers in Dayton, Ohio about energy and home comfort issues (specific to HVAC systems). 

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