Hissing sound from air conditioner unit

When turn on the a/c, there will be hissing sound comes from inside dashboard every 1 minute interval, and the air blown somehow not cool as usual.
Another problem is water drop (under bonnet) comes out from a/c system also quite often/a lot compare to normal car air conditional unit.
Compressor sound from engine also quite often, it is synchronized with the hissing sound comes from dashboard.


Is there any problem with cooling coil or thermal expansion valve?
Could you suggest me