Continuous thumping will mean that there’s something not working correctly in your unit.

Most appliances will make some type of noise at various times, like your fridge or the dishwasher spraying dishes. However, if you hear a noise that’s unfamiliar and new, you should pay attention to it.

This guide will go over some of the common HVAC noises you’ll hear from your unit. We’ll also explain what could be causing the noise and what steps you should do next.


Rattling could signify one of the following problems:

  • Damaged Motor: If the motor looks damaged, contact Green Apple Mechanical NJ
  • There’s a Loose Part: Completely turn off the power to your unit and contact a Green Apple Mechanical professional
  • Debris: There may be twigs or another type of material caught in your HVAC’s mechanism
  • Doors or Panels Are Loose: Check the doors and panels on the outside of your unit, tightening any loose screws as needed

If you hear an HVAC rattling noise, see if you can easily determine the cause of the sound. More often than not, you’ll have to contact a Green Apple Mechanical professional company to remedy the issue.

Screeching and Squealing

Have you heard the sound of nails on a chalkboard? What about a fork scratching on a plate? If you hear a sound similar to that coming from your HVAC unit, some of the moving parts could be wearing out and starting to break.

One example could be that the belt needs replacing. The motor bearings may also be damaged, resulting in the motor being slightly off-center.

All of the above items need to be repaired and replaced. Failing to do so could result in your unit shutting down. HVAC maintenance is essential to ensuring this doesn’t happen.


As your HVAC unit powers down, it’s typical to hear some sort of thumping noise. Continuous thumping will mean that there’s something not working correctly in your unit.

If you hear thumping from inside your home, it could indicate:

  • The blower fan is loose
  • The filter is hitting the return grill vent

If the thumping is happening outside your home, the fan might be hitting metal or the compressor springs might be broken. If the thumping happens often and it gets loud, you’ll need to contact a pro to take a look at it.


An HVAC clicking noise can happen for a variety of reasons. One cause could be a problem with the relay process. A clicking noise that’s repetitive could signify an issue with the thermostat that regulates the temperature.

Clicking could also mean that there’s an electrical problem with the HVAC. That could also cause the relay process to stop working.

The contactor is the connection between the compressor unit and the thermostat. Clicking could mean that the contractor needs replacing. A professional from Green Apple Mechanical would need to fix this issue.


A persistent buzzing sound from your outside unit could mean that your unit is freezing up from being used too often. There also might be a refrigerant leak. You can try to see if the issue fixes itself by turning off the unit for several hours.

Your condenser fan malfunctioning could also be causing the buzzing. If the inside fan runs and you hear the buzzing sound from the outside unit, that’ll indicate that the fan is the problem.

The sound could also be caused by an electrical problem. A repair company will need to come out to evaluate the cause of the buzzing sound.


If you hear a “thwapping” sound, that could mean that there’s something stuck in your HVAC’s blower’s fan blades. If the noise comes and goes with the unit’s airflow, that could help you determine if that’s the problem.

This problem might not play a critical role in how your HVAC functions, but the object that’s causing issues could result in wear and tear on your HVAC unit.


If the heat hasn’t been run for a while on your HVAC unit and the popping sound is coming from the ductwork, that’s a common sound. It’s a result of the colder metal ducts expanding from the warm air entering the ductwork.

If the popping doesn’t go away or comes from another source, you’ll need to call a Green Apple HVAC technician to figure out what’s going on.

Screaming or High-Pitched Whistling

High-pitched whistling or screaming is a warning sound. If the sound is coming from the compressor, you need to move fast. Turn the power off to the unit immediately.

Those sounds could also mean there’s a very high refrigerant pressure or your compressor is helping. It could also signify there’s an internal link.

Regardless of the issue, you’ll need to get a Green Apple professional help to fix the problem.


If the hissing is coming from your furnace, that typically means there’s a leaking air duct. That could mean there’s a leak that needs Green Apple professional repair work.

If the compressor seems to be making a hissing sound, that could signify there’s an internal refrigerant leak. That could also mean there’s high internal pressure. Turn off the power to the unit and call Green Apple Mechanical NJ.


Booming sounds occur when the furnace is trying to light or relight an electronic ignition or pilot light, but having trouble. This results in an increased build-up of gas inside of the combustion chamber that could ignite all at once.

This isn’t something you want. Contact Green Apple Mechanical to fix the issue.

Don’t Let HVAC Noises Turn Into a Serious Issue

Any unordinary HVAC noises should be addressed immediately. Many of them could be a sign of a more serious issue. Failing to act on them quickly could result in the failure of your unit. Green Apple Mechanical NJ are the experts you can trust. We have been serving the New Jersey area for years with professionalism and expertise. Customer service and care are always our number one priorities. If you have any questions or concerns regarding any of your HVAC needs call us today toll-free at 888-611-7191

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