Foreign Object Falls into the Outdoor Unit
Another issue that can cause loud noises from the outdoor unit is the presence of foreign objects inside. Similar to the third cause, but instead of dirt buildup over time, a foreign object may suddenly fall and get stuck inside, such as a mouse, lizard, etc.
This can result in unpleasant odors and loud noises from the outdoor unit. If you suspect this has occurred, it is crucial to investigate and address the issue promptly.

Malfunctioning Outdoor Fan
During the rainy season, the outdoor fan often has to operate continuously and is exposed to rainwater. This can lead to the rainwater drying out the lubricating oil in the unit, resulting in annoying noises.
Additionally, the fan may be broken, causing it to spin off-axis. Sometimes, the internal wires in the outdoor unit may hit the fan, creating a loud noise.
Damaged or Missing Rubber Pads
One of the most common reasons for a loud and vibrating outdoor unit is damaged or missing rubber pads underneath the base. As they are constantly exposed to outdoor elements like sun, rain, and wind, these rubber pads can become hardened, rotten, or completely lost, reducing their ability to dampen vibrations.

Moreover, if the fixing base screws are loose, the force of the rotating fan can create strong vibrations and loud noises. In this case, simply tightening the screws or replacing the rubber pads should restore quiet operation. However, if you discover that the technician forgot to install the rubber pads initially, this is a serious oversight that should be addressed immediately to prevent future issues.
Dirty Outdoor Unit Due to Lack of Maintenance
The outdoor unit, being exposed to the elements, can easily accumulate dirt and grime if not cleaned regularly. Over time, the buildup of dust and debris can cause internal components to function less smoothly, leading to increased friction and loud noises. Therefore, regular cleaning of the outdoor unit not only ensures quieter operation but also prolongs the lifespan of your air conditioner.