Did U do any servicing on the Air Con ?
I suspect after i done a servicing, this thing happen
Maybe due to the chemical ...
hmm.... i oso suspected a little about the air con servicing.
yes, i took up the aircon servicing plus air filter change before this happened.
Think the chemical wash may have corroded the cooling coil

One of the things in the package is
- Prevent unwanted accumulations of unhealthy foreign particles on cooling coil & drainage system