My Air Conditioner Is Making a Pulsating Noise

Nothing strikes fear into my heart more so than when something I own starts making unusual loud noises. This can be a cause for concern and a potential cause to suddenly find yourself in need of some extra hours at work.

Thankfully, in the case of your air conditioner making a pulsating noise, the common causes are easy to address and fix. A pulsating ac unit at its root is caused by the compressor’s actions and is additionally either caused by the unit sitting on an unsolid platform, a loose fan component, a bad capacitor, or by an uninsulated lineset coming in contact with something. 

Unsolid Platform

A compressor sitting on an uninsulated platform, namely plastic platforms, have a tendency to make a pulsating noise. This occurs when the air conditioner’s compressor reverberates through the plastic base which in turn makes a pulsating sound.

This problem can be fixed by switching out the platform that your air conditioner sits on. I recommend either a level wooden platform or a concrete slab variant. Both of these not only last longer than plastic platforms, but they produce almost no noise.

Uninsulated Lineset

The refrigerant lines that connect to your air conditioner unit are supposed to be insulated but sometimes this insulation becomes torn or damaged during installation.

The compressor within the air conditioner uses these lines to move refrigerant – when this is happening, the compressor’s actions are reverberating through the entire length of the lineset. 

Since this is the case, if the bare uninsulated refrigerant line comes in contact with any other surface then it may cause a pulsating or humming sound.

Loose Fan Component

In addition to the pulsating sounds that can be attributed to the causes above, if you hear a metallic pulsing or buzzing noise coming from the fan in your heating and cooling system then it has a loose fan component.

This can often be tied to the fan motor, loose fan, fan blade, or a combination of all three. This is an easy fix and just requires a few simple steps. If the sound is not loud enough to be heard inside you should still take the time to ensure everything is tightened.

  • Remove the top of your air conditioning unit to expose the fan.
  • Tighten down all of the loose parts that hold the fan together – this includes the fan blades themselves.
  • Replace the cover to the air conditioner.

Bad Capacitor

This problem is easy to detect because if there is a bad fan capacitor in your air conditioner then the unit’s fan won’t kick on. A pulsating sound will be caused when the fan tries to start but is prevented by a bad capacitor. This fix is more intensive so I recommend contacting a licensed HVAC technician to address and repair the capacitor.

Bad Compressor

While the compressor can cause a pulsating noise by causing other parts to vibrate, it can also be the root cause of the problem. If your compressor is out, a lack of cold air would also be present with the pulsating sound. If this is the case you could potentially be out $1,500-$2,000.

This is why you should call around, to ensure you are getting the best price for the job.


A pulsating sound coming from your air conditioner can be caused by a number of things. Above is a list to help you troubleshoot and locate the exact problem.

If you are still having trouble pinpointing the exact issue then you should contact a licensed professional right away to come out, address, and fix the issue.