Aiya.. DD bus on 147 alwayz have that problem de.. the moment
that the Upper Deck is packed, it will be very stuffy and HOT..
just move to the lower deck.. although you dont get to enjoy the
scenery around you but at least you got the Aircon... if can, try
to wait for a Mk2 147.. their AirCon is Powerful... or a VO3x
(95xx-96xx)