Aircon still smells bad after cleaning – what could they be missing?

Hi all,

I just moved into a new place and noticed that the aircon smells bad when I start it. It’s a 10-year-old model. I requested the management company to have it cleaned, and a person came over and did a cleaning using high-pressure water.

It seemed fine for a while, but after about 2 weeks, the smell is back. It has a wet-towel type smell and only lasts for the first 3 minutes after I start the unit.

Does anyone know what parts of the aircon might not have been properly cleaned last time? I want to tell the cleaning crew what to focus on this time. Or is it possible that with a 10-year-old aircon, there’s no way to get rid of the smell completely?

Thanks in advance!