@air explorer bro i think there are no indication but my family thought ac is not working though i didnot agree it was fine
but still had to take it. Usually throw of ac gets reduced with time maily due to blockage of evaporator due to dust just like home ac..... and there the role of filter comes in if there is filter u can just clean it at home with out getting in to this service mess.....
@about no ash tray its good na may be they are promoting no smoking :P.