There are two types of symptoms why your aircon is producing a foul smell.

1. Air Con that smells like “smelly sweat” coming out the first 10 minutes but disappear after that
   • The condensation on the coil are not dripping off to the drain pan. The condensate sticks on to the coil and during the next round of operation thus causing the “smelly swear” smell

Solution: Turn on the mold proof function of your AC device, if you do not have this function, manually turn it on to FAN mode and let it run for 20 minutes to clear off any excess condensate. This helps to get rid of the smell. 

1. Air Con that constantly producing a smelly smell (This usually happen after a long period of time)
   • There is a scent freshener in the room and during aircon operation, it get mixed in with the indoor unit and this get stuck on the coil
   • The drain pipe is choke with dirt or located near a place with pollutant or odour that is producing a foul smell, the air get sucks in and circulate into the room

Solution: You need to find the source of the problem first before performing a chemical wash as this will only temporarily remove the smell that get stuck on the coil. It will come back to you again after awhile.