Although modern air conditioners are quieter than older systems, you’ll still typically be able to hear at least some noise when your AC runs. You’ll almost always be able to hear the blower inside your house, and you might also hear the sound of the AC condenser outside running when in any room near it. While hearing some low-level noise is normal, excessive noise or unusual sounds indicate that your air conditioning has some type of issue and likely needs to be repaired. In this article, we’ll look at the most common issues that can cause an AC system to run loudly or make unusual sounds so that you know what to do in this situation.
Loose Parts
If you hear a rattling noise coming from the AC condenser unit outside your house, one of the components could be slightly loose, which means you need to have a screw or bolt tightened. This often happens over time as a result of the vibrations when the unit runs. A loose screw or bolt isn’t necessarily a serious issue, but there is a risk that it will eventually come out.
Another possibility is that the condenser fan itself isn’t tightened. This is potentially a more serious issue since it can lead to the fan not being properly balanced. That can then result in the fan blades scraping or grinding against the cabinet, which can damage or bend the blades or even cause the fan motor to burn out.
AC Unit Isn’t Level
Another reason your AC may be making a loud rattling noise is that the unit isn’t sitting level on the concrete or composite pad. If the condenser unit isn’t level, it will vibrate excessively. Excessive vibration often leads to increased wear and tear and can also potentially cause one of the refrigerant lines to come loose and the system to leak. Because a lot of these issues need to be handled by a professional and can lead to bigger problems, have a technician inspect your AC as soon as possible any time it starts making a rattling noise.
Malfunctioning or Worn-Out Motor
A humming or buzzing sound is often related to one of an AC system’s motors. For instance, the compressor or the condenser fan motor in the outside unit will usually start producing a noticeable humming noise when it begins to wear out. The fan motor will also usually make a humming sound if the fan blades are jammed by debris or the fan isn’t spinning.
Repairing or replacing the condenser fan motor or the entire fan assembly is a fairly simple fix. If the compressor itself is starting to wear out, however, it generally indicates that your AC is on its last legs and you’ll need to replace it fairly soon. While you can replace the compressor, the high cost of doing so means you’re usually better off just upgrading to a new system.
Electrical Issues
A buzzing sound can also indicate that your AC has an electrical issue. Electrical issues like a loose wire connection or frayed wire can be extremely serious since they can result in major damage. At their worst, they can even lead to the condenser catching fire. For this reason, we recommend shutting your air conditioning off if the condenser makes a buzzing sound and leaving it off until a technician has inspected it.
Worn-Out Bearings
A squealing or screeching sound usually indicates that the bearings in one of your AC system’s motors are wearing out and need to be replaced. If the noise is coming from outside, it is either the bearings in the compressor motor or the condenser fan motor. If the sound is coming from inside your house, the bearings in the blower motor are likely to blame. Most motors have sealed bearings, but some need to be lubricated regularly. As such, the noise can mean you need to have the bearings oiled rather than repaired.
Replacing or lubricating the bearings is another fairly easy fix, but it is something you need to schedule immediately. The motor can easily overheat and get destroyed if the bearings completely wear out.
Bent Fan Blade
A grinding sound from the outside AC unit is often caused by a bent fan blade that is scraping against the cabinet. As we said earlier, this is a serious issue since it can cause further damage or lead to the fan motor burning out. In some cases, the blade can get stuck and prevent the fan from spinning. This creates an extremely high risk of the motor burning out. Even worse, the compressor can suffer major damage if your AC runs when the fan isn’t spinning.
You should easily be able to look and see if the fan is scraping against the cabinet when the unit is running. You can also check to see if any of the blades are bent when the unit is off. If you see that a blade is bent or scraping, you should keep your air conditioning shut off until you can have a technician fix or replace the fan.
Loose, Damaged or Misaligned Blower
If you hear a scraping sound coming from the indoor part of your AC system, it usually means that the blower is loose, damaged, or not properly aligned. Any of these issues can lead to it scraping against the housing surrounding it, resulting in a loud noise that sounds like metal grinding against metal. As with the previous issue, you want to shut your AC off to avoid causing further damage or the blower motor burning out.
Dirty Air Filter
If you notice that the blower is running more loudly than usual, the first thing to do is check to see if the air filter needs to be replaced. Changing the air filter in your AC system regularly is important for many reasons. One is that a dirty air filter can greatly decrease the energy efficiency of your AC system and make it work less effectively, resulting in your comfort suffering and your energy bills increasing. Another reason a dirty air filter puts additional strain on the blower is that it has to work harder to draw air in through the filter, which can cause it to run more loudly. This can result in the blower having a shortened lifespan or burning out due to overheating.
Clogged Blower
The air filter in an AC system traps dust and debris and prevents them from getting into the air handler where the blower is located. Nonetheless, some dust still ends up getting inside and starting to collect on the squirrel cage surrounding the blower. This is one reason why annual AC maintenance is important since the technician will always clean the blower. If the blower gets caked with too much dust, it won’t work nearly as effectively as it should. As with a dirty air filter, the result is that the blower has to work harder and may start running more loudly.
Joyce Cooling & Heating Inc. is a family-owned business serving the Nashua and Canterbury areas since 1995. We offer the full range of residential and commercial HVAC services and are always here to help if you need any AC repair or heating repairs, installation, indoor air quality testing, or maintenance services. Contact us today if you need to have your AC inspected or to schedule any other service.
