When your air conditioning unit gets going on those hot summer days, it can get pretty noisy. This is especially true for older HVAC system models that seem to make a ton of noise just to get started. But hearing a lot of clanking and banging isn’t usually a sign of distress for your unit, nor does it necessarily suggest that you need HVAC repair. However, knowing what to listen for is important. When your unit starts up, you might be put off at first by the sheer amount of noise coming from the machine, especially if you’re trying to cool down your bedroom at night to prepare for sleep. If you’re worried about your HVAC making a ton of odd noises, here are a few common noises you’re bound to hear when your air conditioner is going strong.

1. Banging

One of the most common noises you’re likely to hear with your HVAC unit is soft to loud banging. This might start up right as you’re firing up your machine, or it may occur later. Either way, banging isn’t necessarily a sign of something serious having gone wrong. However, if the banging you hear is continuous and doesn’t go away after a few seconds, it could be a sign that something is loose in your machine. This could be a smaller part like a connecting rod or a larger part that’s broken off, causing your machine to work less efficiently. It could also signify that you need a new part to aid your machine, like a compressor replacement.

2. Clanking

If the banging you thought you heard starts to turn into a clanking noise, it could be an indicator of more serious trouble ahead. As with banging noises, a clanking sound could indicate that a part has broken loose inside your machine. If could also indicate that something has loosened just enough so that it stays in place but keeps brushing against other parts of the machine, like the fan or two loose pipes. In any case, you don’t want to let the situation go unresolved for too long. Even if everything is still is working condition, having loose parts rubbing together in your machine can end up causing some major damage to the unit over time.

3. Rattling

If you’re hearing rattling in your HVAC unit, don’t panic. A rattling sound usually means that something small is stuck in the passageway between your unit and the outside of your home where it connects to its power source and doesn’t take too long to fix. While rattling usually indicates an obstruction in your machine, it’s usually originating from the outside of your machine’s tubing or vent, not from within the unit itself. While this still requires professional attention, it’s a much less invasive problem than a loose part or broken piece. Your machine may have a small blockage inside the tubing that connects it to the outside of your home, such as a twig or a clump of leaves. If the rattling persists, call a technician to come and remove the obstruction from your machine.

4. Hissing

To deal effectively with hissing, you’ll first need to identify where the exact sound is coming from before trying to address the issue. If the hissing is coming from the unit itself and is a softer sound, it’s most likely coming from your machine’s air vents. When hissing occurs, air that should be circulating from your machine is leaking. If you’re hearing a louder hissing sound that’s coming from the walls surrounding the unit, you have a duct issue. Either way, fixing the leak is crucial in order to keep your machine working properly rather than using up a ton of energy and wasting air.

5. Screaming

If you’ve heard your AC unit scream, as opposed to hissing or squealing, it’s a sign of a big problem. When your unit screams and makes a loud high-pitched sound, discontinue use immediately. Screaming often occurs when the pressure has started to build up in your machine past the point of danger. In order to assess the damage, you’ll need to call in a professional as soon as you. Even if the screaming sound ends up not being linked to pressure-related issues, it could be a sign of a leak that could seriously affect the air quality in your home and end up doing serious damage in terms of air pollution in your space. Don’t take chances when you hear screaming or high-pitched noises of any kind coming from your unit. Resist the urge to tamper, and always let a professional handle it instead.