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Why Is My AC Making Loud Noises?

Tired of your AC making loud noises?

Is your AC system suddenly making strange, loud noises? You’re probably wondering what’s causing them and if you should be concerned.

While it’s normal for an AC system to produce some noise as it starts up and to gently hum while it’s running, there might be a more severe problem if you start hearing loud, odd noises you haven’t heard before.

Typically, when HVAC technicians repair a noise problem, they’ll first inspect what kind of sound the AC is making. The 3 most common types of noises that indicate a deeper problem include:

If your AC is making one of these noises, you should call a professional HVAC technician immediately to schedule a repair to prevent any significant issues from impeding its operation.

Want to resolve your AC noise issue ASAP?

Contact Climate Design at (727) 592-5040 or schedule below! We offer same-day AC inspections and repairs, and we’re available from 8am to 8pm all week long—including Saturdays. Our NATE-certified technicians can perform to the highest of industry standards and will efficiently diagnose your system to find the root issue.

Hissing and Whistling Noises

Hissing or whistling noises coming from your air conditioner could indicate that your AC has either a refrigerant leak or poorly designed ductwork.

First, let’s cover how a refrigerant leak leads to a hissing noise.

Refrigerant is a chemical agent that plays a vital role in cooling your home. It circulates between your AC system’s indoor and outdoor units in a closed-loop system via refrigerant lines, absorbing warmth from your home’s indoor air to disperse it outdoors.

However, when there is a leak in the refrigerant lines or AC units, a hissing sound occurs when air and refrigerant make contact.

If there is a leak in your AC’s refrigerant lines, you will hear a strange hissing sound.

You may have a refrigerant leak if:

  • You’ve noticed warm air coming from your AC vents
  • You’ve noticed your energy bills increasing despite normal usage
  • You’ve noticed your AC takes longer to cool your home or starts up more frequently

Solution: Think you might have a refrigerant leak? Contact a professional HVAC technician straight away to inspect your unit, repair the leak, and recharge the refrigerant. You should not attempt to do this yourself because refrigerant is a toxic substance.

Now, let’s cover how poorly designed ductwork can lead to whistling noises through the air vents.

Air ducts that are not big enough or have too many sharp bends increase the air's velocity and the amount of air getting pushed through them. Either scenario increases noise.

You can tell if you have poorly designed ductwork if:

  • Your home feels stuffy
  • You can see mold growth on vents
  • Your doors frequently slam closed by themselves

Solution: When your home has a faulty ductwork design, contact a ductwork expert to inspect the system and determine if it needs a partial replacement or total redesign.

Clicking and Buzzing Noises

Loud clicking and buzzing noises are an indication of issues with your AC system’s electrical components, such as the following:

  • Control panel
  • Thermostat
  • Electrical wiring
  • Capacitor
  • Contactor

Control Panel Problems

The AC system’s control panel may have faulty electrical signals that create clicking noises or tiny sparks of electricity. If you notice clicking noises or electrical sparks, turn off your system and call a professional HVAC technician right away.

Thermostat and Electrical Wiring Problems

Buzzing noises can occur when you change thermostat settings, indicating the thermostat has a faulty part.

If you see constant sparks, that indicates that electrical wiring in the system is either loose or exposed, creating a discharge.

When an electrical wire doesn't properly connect to the AC’s circuit breaker, it will make continuous buzzing noises.

Other reasons for a buzzing noise include:

  • Your AC’s refrigerant lines are leaking
  • A thermostat malfunction
  • A broken circuit breaker

Capacitor and Contactor Problems

If the clicking or buzzing noises seem to be coming primarily from the AC’s outdoor unit, its capacitor or contactor may be damaged.

The capacitor is a small cylinder-shaped component that supplies the system with electrical energy, and its juice is vital in helping the system start up. Meanwhile, the contactor is the “switch” that turns the outdoor unit on.

Normally, the AC will click once when it first starts up, but it shouldn’t continue to click. Without a functional capacitor or contactor, the system will try to turn on but cannot, leading to continuous clicking noises. It’s also possible a broken condenser fan motor is causing the loud noises.

Call an HVAC technician to get rid of buzzing noises and keep your AC system functioning normally.

Solution: These clicking and buzzing noises mean that your AC system could fail to turn on or have more severe electrical problems. Call an HVAC technician immediately to diagnose and resolve the issue.

Rattling and Banging Noises

When you hear rattling or banging noises coming from your air conditioner, the cause could be as minor as a loose screw or fastener. Or as major as the fan belt that connects to the motor may be breaking apart.

Loose AC parts may break off and vibrate on the bottom of your unit or against its walls. If the mount that stabilizes the AC’s blower wheel wears out, for example, the fan can wind up slamming against the unit’s casing.

A broken or incorrectly mounted AC compressor can cause loud banging noises.

Another more serious reason for banging noises could be a broken compressor or an incorrectly mounted compressor. If your AC system starts shaking when it’s running, you most likely have an issue that needs to be fixed immediately because the compressor is the “heart” of the entire system.

Do you only hear rattling or banging noises when you’re near the AC’s outdoor unit? The following problems could cause them:

  • Leaves and twigs lodged inside of the unit

  • Fan blades can wear out over time, causing the fan to come loose and slam against the inside walls of the unit

  • The screws that hold the panels of the outdoor unit together may be falling out

  • The springs that hold the refrigerant pump in place could break, causing the pump to hit the compressor

Solution: Contact a technician to replace, adjust, and clean AC parts as worn-out loose parts can cause more parts to break down.

Concerned about the mysterious noises coming from your AC? Contact Climate Design.

No matter the AC brand or the time of day, we can help you make your home quiet again. We provide service from 8am to 8pm all week long.

Our technicians are NATE certified, which ensures we will perform AC repairs to the highest of industry standards. We have over a thousand 5-star customer reviews that showcase our commitment to great customer service and technical excellence. Call us for service today or schedule below.