Q: air con fan is very loud

It sounds like you could be having an issue with your A/C fan. The A/C fan is responsible for keeping the engine cool when the A/C is on. When the A/C is running, the engine will create more heat as it must exert more effort to power the A/C compressor. It is possible that the compressor malfunction causes the fan to cycle all the time. It is more likely however that the fan motor itself is going bad slowly. Electric cooling fans will typically get louder before failing all together. This is because the bearing in the middle that keeps the fan blade spinning freely has failed. I would recommend having a certified professionial, such as one from YourMechanic inspect your A/C fan with a mechanic’s stethoscope to determine if the sound is coming from the fan bearing. If the fan bearing has failed, I would recommend having the electric cooling fan replaced.