I keep hearin perdiodic a few seconds long hissing (?) "pshhhhh" noise out of my AC.It is very pronounced right after car starts but continues all the way to freeway speed. Turning ac off (with fan running) or fan off gets rid of the noise. I am not sure if it is relevant but noise started right about after alternator and its belts got replaced.
What can it be? Should I take care of it immidiately?