9 Noises Your AC Should Never Make

Today, air conditioning units are manufactured to be much quieter than their predecessors. Many models use sound dampening technology and two sound compressors, so it’s easy to notice that something is not right when your new AC unit makes weird noises.

As one of the top air conditioning companies in Roseville, we have compiled a list of some weird AC noises and what they mean.

Banging or Rattling

A banging or rattling noise coming from your unit could mean that a compressor part is loose or damaged. An unbalanced indoor blower or a dislodged motor mount can also cause a banging noise.

A loose or damaged part can affect other parts, increasing the amount of stress on them, which in turn will impact their performance. Too much stress can shorten your unit’s life expectancy.

If you hear a banging noise coming from your unit, act fast. Check your AC’s compressor. Tighten loose compressor parts. Remove any debris such as leaves, twigs, and dirt and dust particles stuck in them. If your compressor is damaged beyond repair or nearing the end of its service life, it makes sense to replace it.

If you hear a rattling noise all over your home, either your ductwork was improperly installed or a ductwork section has become loose. Make sure all of your vents are opened as closed vents can cause leaks or can become loose due to pressure differences.


A high-pitched screeching or squealing noise coming from your unit could indicate a loose or damaged belt. Other possible causes include unusually high pressure in the compressor and faulty fan bearings.

Do not wait too long to fix the problem as a loose or damaged belt can break. Without a functional belt, your blower won’t turn. Thankfully, it is usually inexpensive to repair a damaged AC belt.


AC units make clicking noises whenever they are turned on or off. This is a normal part of AC operation. However, constant or ongoing clicking could mean there is something amiss. A clicking noise coming from your unit could indicate a failing thermostat or problems with the electrical controls.

An obstruction in your unit’s fan can also cause a clicking noise. Turn off your AC and check your condenser to see if an object is obstructing the fan. If your AC won’t start and makes a clicking noise, there could be an electrical problem. Have your technician inspect your AC as soon as possible.


A hissing noise is a common sign of refrigerant, compressor valve, or duct leaks. High compressor pressure can also cause a hissing noise. Do not ignore the problem. Have your expert air conditioning technician investigate the issue right away.


There are several issues that can cause a buzzing noise. A buzzing noise could mean the following things:

  • Some parts of your AC have become loose
  • One or more of your AC filters have become clogged and should be replaced
  • You have an electrical issue, or your contactor relay switch, fan motor, or circuit breaker is failing
  • The condenser line has become clogged with dirt and needs to be cleaned
  • A failing blower

If you hear a buzzing noise coming from your unit, reach out to a Roseville air conditioning company for help immediately.


A humming noise could mean your capacitor or motor is failing. Electrical problems, vibrating pipes and loose parts can also cause a humming noise. If your compressor does not start and makes a humming noise, there can be an issue with your motor. Though these are minor problems, they should be addressed in a timely manner or else they could lead to major issues.


A high-pitched squealing noise can indicate a damaged compressor that is most likely due to high internal pressure. Though air conditioning units have sensors that sense high pressure and shut them down when the pressure exceeds the maximum allowable limit, these do not always operate if damage. Shut off your AC immediately if you hear a squealing noise and call your technician.

A low-pitched squealing noise means it’s likely your fan belt has worn down or is misaligned or damaged and needs to be replaced. Have your technician replace the belt before it snaps and your AC stops working.


A high-pitched screaming or whistling noise coming from your unit could be a sign of a refrigerant leak or high internal pressure within your unit. Some other common causes of a whistling noise include dirty air filters, leaky ducts, blocked return vents, and closed dampers.

Change your filters and make sure your vents are not blocked by furniture or other items. If the problem persists, call your technician.

Bubbling or Gurgling Noise

More often than not, a bubbling or gurgling noise is caused by a refrigerant leak. A bubbling noise could also mean that your condensate line has become clogged. Ask your technician to clear any blockages as this is a job best left to the professionals.

At South Placer Heating and Air, we are committed to helping homeowners get the most out of their heating and cooling systems. We are your go-to team for AC repair, maintenance, replacement, and installation. To learn more, call (916) 246-2089.