update:

just want to be assured na aircon problem na lang ito.

with the aircon turned off, everything is normal na.

with the aircon turned on, sometimes there is a whistling sound that can be heard coming from the aircon vent. when this is heard, humihina ang hatak ng kotse. when this sound turns off, normal na ulit ang takbo ng kotse. i'm thinking:

1. kulang sa freon
2. may butas sa hose (thus nababawasan ang freon)
3. high pressure