Winter is coming to an end, and that means that the central air conditioning system in your home will soon be getting a workout. Unfortunately, after long months of fall and winter inactivity, air conditioning systems do not always work as they should. Even if you have kept up on all your routine maintenance and spring cleaning, AC systems sometimes fail or work less efficiently than they should. Although sometimes the first sign of trouble will be a system that fails to cool your house properly or at all, other times you will get warnings in the sound of unusual noises.

Loud Bangs from the Ductwork

If you are hearing loud banging noises that seem to originate within your home's ductwork, there are a number of possible causes. Luckily, this type of noise usually does not indicate a serious problem with the outside AC unit or any other major piece of equipment. Instead, the most likely cause is either the ducts themselves ratting or a filter banging up against the opening that it is installed on.

The first step is to check your filter and confirm that it isn't too dirty. If it seems dirty and the filter is washable, then give it a good cleaning and see if the problem goes away. If your filter is not reusable or you are unable to clean it well, replacing the filter is another good option. Anything that restricts airflow through the filter can cause the air conditioner to pull the filter against the opening that it is installed in, resulting in a loud thud or bang. If the filter seems out of place at all, then this is most likely the noise you are hearing.

If the filter doesn't seem to be the problem, check the fan on the indoor AC unit located near your furnace. It should be fairly easy to determine if this is the problem, as you should be able to listen from nearby the indoor unit. If this is the source of the noise, the blower unit may need to be professionally repaired.

Exterior Sources

Although exterior noises can potentially mean a costlier repair, they are often easier to identify than noises coming from the ductwork. If you are sure the noise is coming from your outside unit, try to listen for the noise from nearby. If you notice the casing or shell of the unit rattling, then it is possible that the noise is simply a loose bolt or screw. The bolts on the outside of your AC unit are easily accessible, so tightening them is a straightforward do-it-yourself job.

If this doesn't solve the problem, then the most likely culprits are the compressor or fan. Fortunately, this doesn't necessarily mean that one or both need to be replaced. Low refrigerant levels can cause bangs or other loud noises as the compressor comes on, so it is possible this is the source of your problem. Whatever the case, if the thud or bang seems to be originating from the main unit then you should contact an air conditioner service professional to perform a thorough inspection of the unit and the rest of your central air system.