During the Halloween season, you and your family love to make spooky sounds. You moan like ghosts, screech like witches, and groan like zombies. But when you’ve tucked yourself in for the night, you look forward to a peaceful, undisturbed sleep.

Unfortunately, your air conditioner seems to have taken the Halloween spirit to heart. Long after you and your children stop giggling, your unit continues to rattle, thump, clang, and bang. And some of these noises are enough to scare away the typical things that “go bump in the night.”

Are these spooky sounds something to worry about?

1. Screeching and Squealing

When your air conditioner turns on, does it make a loud, high-pitched screech? Or does the metal-on-metal sound much like a train stopping in its tracks?

If so, the screeching could result from one of two damaged parts:

  • The fan motor, or the blower, blows air over evaporator coils. If the fan has a bad belt or bearings, the friction will cause the fan to vibrate and screech as it turns.
  • The compressor condenses the refrigerant in your system, which in turn cools the air. Like the fan, the compressor has a motor with a belt that could rub the rest of the machinery the wrong way.

In either case, these parts will need replacement and lubricant to ensure the system runs smoothly and quietly.

2. Clanking and Banging

Does your air conditioner sound as though a poltergeist is hammering its way out of your unit? Your imagination isn’t too far off from the real thing.

Your air conditioner compressor consists of multiple parts screwed and bolted together. When one of the screws, rods, pins, or crankshafts come loose, they often vibrate and bang against each other. In some cases, the parts break completely and disconnect inside the compressor, rattling around until they can find their way out.

Unfortunately, most compressors come hermetically sealed (airtight). So these pieces will continue to bounce around and damage your machine. The only way to silence this noise is to replace the compressor entirely.

3. Thwapping and Thumping

Have you ever tied a playing card to a spoke of a bicycle tire? As the tire turns, it makes a distinct “thwapping” sound every time the card contacts the spoke.

Your air conditioner may make a similar noise when something lodges near the blower blades. As the fan turns, it contacts the debris, creating an unmistakable thump. And the bigger the debris, the louder the noise.

Though the problem isn’t serious, it can put extra wear and tear on your motor. The motor has to work hard to push the fan blade past the obstacle. To extend the lifespan of your unit, you’ll want an expert to remove any dirt, dust, and debris in your machine.

4. Hissing and Bubbling

Does your unit make a faint hiss or a more pronounced gurgle?

In general, most air conditioners do make a faint, temporary hissing noise, even when newly installed. As refrigerant expands in the expansion valve, the gas hisses for a second or two and then goes away. This is a normal part of the cooling process.

However, if you hear a more persistent, bubbling noise, the unit may have sprung a leak. As refrigerant remains under constant pressure, it will squeeze its way out of any available exit, including pin-sized holes and cracks.

As cracks and leaks tend to happen more often to older cooling systems, you’ll likely want to replace the entire unit rather than track down all the holes and cracks in the lines.

What Can You Do?

If your air conditioner makes any of the above sounds, talk to your local HVAC technician about the problem. He or she can then diagnose the source of the sound and recommend repairs or replacement. With professional help, your air conditioner will stop haunting your evenings and let you rest in peace.