I know this is quite old thread but for the sake of others, I wanna advise you all guys to stay away from NISSAN Islamabad Motors. All of their mechanics left them and just one is there now a days. The entire team is totally technically illiterate and just learning by hit and trial method applying on your cars. There's no rates/prices deciding policy and their rates are extremely unfair, many times more than local markets.
For Good AC mechanic in Islamabad, read this thread:
https://www.pakwheels.com/forums/mechanical-electrical/145640-universal-car-ac-g8-islamabad-honest-man