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Why Heat Pump Making Loud Noise in Cold Weather


Why your heat pump makes loud noises or strange sounds in winter? This is due to the accumulation of ice on the fan blades, which can cause serious damage to the heat pump. It is best to shut down the equipment and run the emergency heat source (e.g., furnace) until the ice on the outdoor fan melts. Your heat pump also has a defrost mode, and we will explain how the defrost mode works and the possible reasons for its malfunction.


What causes the loud noise in the heat pump?

If your heat pump makes noise after snowfall in winter, the possible reason is the accumulation of ice on the external fan blades. It’s similar to how a car wheel makes noise and vibrates slightly when it’s slightly unbalanced. When there is ice on the fan blades, you will also notice vibrations in the heat pump cabinet.


Examples of a noisy heat pump:

Here are some visuals and sound examples of an actual heat pump with ice on the external fan blades.


What to do when the heat pump fan freezes:

When your heat pump makes loud noises in cold weather, please shut down the heat pump.


Sometimes, the noise from the heat pump may be subtle, but the impact of the ice on the fan blades can be significant. Due to excessive ice buildup, you may lose and completely tear off the fan blades.


Therefore, shut down the heat pump to allow it to thaw. Use the emergency heat source instead. This should provide supplemental heat, such as a gas furnace.


heat pump installation
Why Heat Pump Making Loud Noise In Cold Weather

What is the defrost mode in a heat pump?

The defrost mode is a normal cycle that the heat pump goes into. Every 60-90 minutes, the heat pump asks itself, “Do I have ice?” If it does, it essentially puts your equipment in emergency heating mode and activates the air conditioning mode on the outdoor unit.


When in defrost mode, you will hear a swooshing sound.


You may feel a bit of cool air as the air conditioning actually turns on for a few minutes before returning to the heating mode.


Is it normal for a heat pump to frost up?

Occasionally, a little bit of frost on the heat pump is normal, but severe ice or snow buildup is not normal.


Types of heat pump noises:

Hissing sound:

The heat pump contains a valve that reverses the flow of refrigerant when switching between heating and cooling. In cold seasons, the heat pump switches to defrost mode, and the valve reverses, creating a hissing sound that lasts for a few seconds. After the swooshing sound, the compressor makes a slightly louder sound.


This sound is normal and may seem louder in winter when the heat pump works hardest. However, if the sound persists throughout the entire operation of the heat pump, consider contacting a professional.


Loud metal-on-metal noise:
This type of noise may occur when it’s cold outside and is likely caused by the fan blades hitting ice chunks, fan components, or loose wires. If you hear such noise, immediately shut down the equipment to prevent further damage and contact an HVAC technician for inspection and repair.


Clanking and intense vibration:
Over time, clanking noises and vibrations may intensify, indicating loose screws on the cover plate or other hardware components. The sound may also come from refrigerant pipes that are binding. Some heat pumps tend to be louder than others, so you either have to get used to the noise or consider replacing the equipment.


Screeching noise:
This type of noise, resembling the sound of a vehicle belt, indicates a problem. It could be due to a problem with the blower fan belt or its bearings, leading to screeching or squealing noises. Contact a technician for maintenance, repair, or replacement if you encounter such noise.


Clicking, humming, and buzzing:
Rapid clicking, especially accompanied by humming, indicates electrical issues with the heat pump. The sound may come from worn-out electrical components or loose connections. If you hear such noises, shut down the system immediately to avoid further electrical damage and complications and contact an HVAC technician.


Hissing or gurgling sound from the heat pump or pipes also indicates a problem. It could be refrigerant or air escaping, which is a major issue. Once the refrigerant level becomes low, the heat pump will fail to transfer heat to your home.


Such issues are difficult to troubleshoot on your own and may require professional assistance for proper diagnosis and repair. If you notice hissing sounds, shut down the heat pump immediately and contact a technician.

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Noise when turning on or off:

Furnaces make noise when turning on and off, but over time, the sound becomes familiar. For new users of a heat pump, these sounds may seem strange and can be mistaken for a problem with the heat pump. For example, some heat pumps include a scroll compass that clicks and clacks whenever you turn them off.


When starting the heat pump, the sound may be loud, and it may seem like the whole system is shaking. However, if you’ve been using the heat pump for many years and notice strange noises when turning it on or off, it may be time to consult a technician.


Humming, gurgling, or rubbing noise:
Humming noise may come from faulty coils or contacts in the heat pump. On the other hand, gurgling noise may indicate low refrigerant levels. Dirty motor bearings can cause a screeching sound.


Such noises require an experienced HVAC technician for proper diagnosis. Many of these strange noises can be eliminated during regular maintenance by a professional. Additionally, your technician can advise you on when to repair and replace the system.

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