Tell a/c wala this problem and ask him if there is any place between grill and radiator where an additional condensor fan could be installed.
Problem with the Mehran is that it comes with only a single cooling fan which work for both radiator and condensor so in summers, it is a common cause of gaskit blown up when running air con.
If problem still persist, tell a/c wala to replace the condensor with a smaller one (i.e. installed in 660cc cars such as terious, mini pajero) so that it could shed some load off the engine.