Asalam O Alykum,
I have got the same problem with my Mehran, 1996 model. But, apart from heating up, it also dries up the radiator water.
Here is what i have been doing since the last couple of months to resolve this, to no avail.
1- Complete Radiator Service
2- Change of all pipes leading to and from the radiator.
3- Relay on the radiator fan
Please dont say the cliche term "mehran is not to be used with ac" i dont afford to get a ferrari now, do i but i have to make use of what i have.....
Any assistance will really really be welcome from my end