Team-BHP - Low FE on Xing with AC on !

hi all,
Guyz i have been facing this problem for quite some time now. During the non AC seasons(hardly any in delhi !) my 2004 Xing returns 11-12 kmpl on local drives. My daily route is the most trafficky route of delhi (ITO chowk) and almost every other day the car is caught for anywhere b\w 15-60 min. in extreme jams, AC switched on all that while.
But the scene changes compltely during the peak summers and even in the (not so hot) end-of-summer seasons when my car starts returning a sad FE of 8-10 kmpl on the same route, under the same conditions. Also, i notice that once i switch on the AC, the engine becomes really stressed and pickup absolutely crashes. Due to which i am forced to be a little heavy footed. I have got my car checked; they say its just because of the heat, the compressor doesnt cut at all, and so the car remains stressed all the time. What is amazing is that w\o the AC on, my car has a gr8 pickup, and returns 16 kmpl on highways, AC on or off ; so there's definitely no prob. with the engine's tuning.

I am really puzzled as to what could be the reason behind this. Kindly help!

Thanks.

You could get the AC condenser cleaned and also get the AC gas checked, other than that i dont know.

I dont find Xing's AC effective in slow moving traffic or while being stationary especially in Delhi's heat. While driving though the AC performs very well.

I get 12-13Kmpl in City driving... with a lot of hard driving as i have a loud ffe!