heat pump

Why Does My Heat Pump Make a Loud Noise When Turning Off?

Do you often get startled by a loud noise from your heat pump as it turns off? You’re not alone. 

When your heat pump makes a loud noise during a shutdown, it could be due to several reasons: the equalizing of refrigerant pressures, issues like the air filter slamming against the grille, ducts expanding and contracting, or components like the fan or compressor encountering problems. 

At Grand Canyon Home Services, we receive numerous queries about this in the West Valley, Arizona. Let’s demystify the issue and explain why this happens.

Normal vs. Abnormal Heat Pump Noises

Understanding the difference between what’s normal and what indicates a potential problem is crucial.

Normal Heat Pump Sounds

Right after the heat pump is turned off, the refrigerant pressures equalize, which can produce certain sounds. The sounds you might hear can be described as:

  • Whooshing or Hissing: This sound is one of the most common noises associated with refrigerant equalization. As the high and low pressures in the system balance out, the refrigerant might flow rapidly between parts of the system, leading to this noise.
  • Mild Popping: As the pressures equalize, the internal components might slightly move or adjust, leading to a mild popping or clicking sound. This is akin to how a car engine might “tick” as it cools down.
  • Gurgling: This sound is similar to water flowing through a pipe. It’s caused by the refrigerant transitioning from a liquid to a gaseous state (or vice versa) and moving through the system’s lines.
  • Some heat pumps may also produce a ‘back-peddling’ noise upon shutdown.

All of the sounds above, when brief and not overly loud, are generally considered normal during the shutdown phase of a heat pump and do not indicate malfunction. However, if these sounds are persistent, overly loud, or accompanied by other unusual noises, it might indicate an issue that requires inspection.

Abnormal Heat Pump Sounds

If the noise from your heat pump resembles a door slamming or metal clanging, it’s time to investigate.

Door Slamming Noise: This noise is sudden, sharp, and loud, much like the sound of a wooden door being forcefully shut. It’s a brief, singular sound but carries a sense of impact.

A loud slamming sound in a heat pump can be due to sudden pressure changes in the ductwork, causing parts of the ducts to expand or contract momentarily. If there’s an automatic damper inside the ducts, and it closes or opens too rapidly, it can produce this kind of sound. Another cause might be the air filter getting sucked up against the grille and then dropping back down when the unit turns off, especially if the filter is dirty or restrictive.

Metal Clanging Noise: This sound resembles two metal objects colliding or clashing against each other. It can be echoing, resonant, and has a metallic timbre. Imagine banging a metal spoon against a metal pot; that’s the kind of sound we’re discussing, although it might vary in intensity.

Metal clanging sounds in a heat pump typically indicate a loose or detached component. For instance, a loose fan blade in the heat pump’s exterior unit might hit other metal components as it spins, resulting in this noise. Over time, wear and tear can also cause screws, bolts, or other fasteners to loosen, leading components to shift and produce this sound. In more severe cases, it might even indicate a broken or malfunctioning compressor spring, causing internal components to knock against the casing.

The abnormal noises above are concerning and can signify underlying issues with your heat pump. If you hear these or any other unusual noises from your heat pump, we recommend contacting Grand Canyon Home Services. Our expert heating repair services are designed to diagnose and address any issues promptly and efficiently. Don’t let those unsettling sounds go unchecked; let our professionals ensure your system’s longevity and optimal performance.

Common Causes of Heat Pump Noises Inside the House

Ceiling vents can cause filters to make noise if they’re restrictive or dirty. Additionally, incorrectly sized ducts can produce noise due to metal expansion. Over time, a loosened blower wheel might bang against the unit. 

Let’s dive deeper.

1. Air Filter Slamming Against The Grille

The problem is common in homes with ceiling return vents. If the filter is dirty or overly restrictive, it might get sucked up and then drop loudly when the unit shuts off.

Solution: Replace clogged filters and ensure the MERV rating isn’t excessively high. If ducts are undersized, consider installing new ductwork.

2. Ducts Expanding and Contracting

If the ductwork isn’t sized correctly for the airflow, the metal can expand and contract, producing noise.


  • Inspect the Ductwork: Have a professional from Grand Canyon Home Services inspect your duct system. A thorough assessment will determine if it’s appropriately sized for the amount of air your heat pump is designed to handle.
  • Properly Size and Install Ductwork: If the ductwork is found to be undersized, consider resizing it to accommodate the airflow adequately. Properly sized ducts not only reduce noise but also increase system efficiency and longevity.
  • Insulate the Ducts: Adding insulation around the ducts can act as a buffer, reducing the noise caused by expansion and contraction. This will also help in maintaining a more consistent temperature throughout your home.
  • Use Flexible Ducts: If appropriate, consider integrating sections of flexible ducting into your system. Flexible ducts can absorb some noise from the expanding and contracting metal, acting as a sort of ‘shock absorber.’
  • Regular Maintenance: Schedule routine heating maintenance with Grand Canyon Home Services. Ensuring that all components, including the ducts, are regularly checked and cleaned can prevent many issues, including noises from expansion and contraction.

3. Fan Issues 

Over time, the blower wheel might loosen, causing it to bang against the unit as it powers down.

Solution: Call heating professionals at Grand Canyon Home Services to inspect the blower wheel assembly.

What Causes Heat Pump Noises in the Outdoor Unit?

Noises from a heat pump’s outdoor unit can be caused by a worn-out compressor spring, resulting in internal components hitting the casing or a loose outdoor fan knocking against other parts. 

Here’s a closer look.

1. Broken Compressor Spring

The compressor has several components mounted on springs. These can wear out, leading to internal parts knocking against the casing when the heat pump turns off.

Solution: A full compressor replacement might be necessary, which can be a significant investment.

2. Loose Fan

If the outdoor fan becomes loose, it can knock against other components.

Solution: Tighten any loose bolts, or consider replacing the fan.

Other Alarming Heat Pump Noises

  • Metal-to-Metal Sounds: Immediate shutdown is advisable. This could indicate fan blades hitting another component.
  • Rattling or Vibrations: While some vibration is standard, sudden changes in noise level can indicate issues with refrigerant piping, loose panels, or other system components.
  • Grinding, Buzzing, or Gurgling: These noises might indicate a low refrigerant charge or dirty motor bearings.

Even if the noises emanating from your heat pump are considered normal operational sounds, no one wants to be constantly reminded of their system’s workings. Thankfully, there are several solutions available to make these sounds less intrusive, which leads us to the next section.

How to Reduce Heat Pump Noise

Consider solutions such as vibration isolation damper mounts, compressor sound blanket wraps, noise-absorbing bases, or relocating your heat pump for optimal performance and minimal disturbance.

  1. Vibration Isolation Damper Mounts: These specially designed mounts can be installed on the bolts holding your heat pump’s compressor. They effectively minimize the vibrations from the compressor, reducing noise output. The dampers act as shock absorbers for a smoother and quieter operation.
  2. Compressor Sound Blanket Wraps: This soundproofing blanket is specifically tailored for heat pump compressors. Made from noise-reduction materials, they fit snugly over the compressor, muffling the sound it produces. These blankets can help with older units that have become noisier over time, and they can also be a proactive measure for newer setups.
  3. Noise-Absorbing Bases: Instead of placing your heat pump directly on concrete or other hard surfaces, consider using a base made of noise-absorbing material. Such bases act as a buffer, reducing the noise generated by the unit’s vibrations and operational movements.
  4. Relocate The Heat Pump: The positioning of your heat pump can significantly impact its noise level. If it’s placed close to walls or windows, the sound can reverberate and seem louder. Consider relocating the unit to a more isolated spot or an area with natural barriers. If possible, keep it shielded from high winds, which can exacerbate noise issues and affect performance.

Final Thoughts on Heat Pump Noises

While it’s common for heat pumps to produce certain sounds, it’s essential to distinguish between usual operational noises and those indicating potential issues. Fortunately, several solutions are available for those regular operational sounds to minimize disturbance. 

If ever in doubt about a sound or performance issue, consulting with professionals like those at Grand Canyon Home Services can provide peace of mind and optimal system functioning. Remember, a well-maintained heat pump is not just about comfort; it’s also about safety and cost-efficiency.

Don’t let unsettling heat pump noises disrupt your peace in the West Valley; contact us today for an inspection!

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