I've had three mehrans since 1994. the first one was a 91 model, second was a 98 and third is again a 98 which i still have and been driving it since 1998. all three did not have a factory fitted a/c and i got the a/c's installed after i bought the vehicles. the first one did not have any overheating issues. in those times back in 1994 the traffic jams were very common. with ac switched on, never faced any problem. the second one was the worst, did all my experimentation on it though. the one i drive now is the result of my experiments on the previous one.
As i understand, there are two temperature issues with mehran. First one as such is not a technical or mechanical issue, it a psychological issue, mehran MAINTAINING A HIGHER WORKING TEMPERATURE, while the ac is on. as long as your vehicle maintains a temperature near, at or slightly above half, it okay. the emphasis is on MAINTAINS.
The second issue is, when the temperature gauge starts to rise and does not stop!!!!!!!! it goes on and on and on until it reaches the top, blows the head gasket or the engine ceases.
anyways, when i installed ac on my second mehran, it ran fine initially, and suddenly one fine morning, the temperature started to rise and blew the head gasket. hmmmm. i got it fixed, and it happened all over again. i consulted all the people and mechanics and a/c guys, no one was able to give a satisfactory answer. BHAI JAN MEHRAN MAIN AISA HI HOTA HAI was the common answer.
so i went to my radiator guy, told him to build me a three line radiator...... didn't work.....
next thing i went to him and asked him to make radiator from a Japanese radiator fins and all.....to my surprise....it didn't work as well......
valve clearance adjustments ......boooh....nothing. its really important though, that the valve clearance is proper....for maintaining optimum temperature.....but in my case didn't work....it valve adjustment did not need correction..
kept on thinking and observing the pattern of heat rise......
lightening struck one day and i had an idea... went to my mechanic and got removed the water pump, it was fine, but still i told him to turn the fins of the water pump a little more so that it may exert a little more pressure and the water may regulate a little faster, stupid though, didn't work as well
was about to give up, when i suddenly noticed that after a regular day run without ac and lights, the car ran fine on ac the next day for at least half an hour and then started to overheat. this got me thinking on other lines. went to the electrician and asked him to fit a relay with the fan, to my surprise he informed me that there was already a relay and the fan was working to its full potential. so i moved on and discussed if i could change the fan, its fins, shroud or motor. the electrician got an ALTO's motor which is larger and more powerful and had it fixed in the same shroud with the old fins. it slightly slowed down the process of overheating, but the problem was not solved. a few days later i had an idea, i went back and told him to check the charging, which he did and was 12 amperes, and he told me that it was fine. i wasn't satisfied. i went back again while the process of overheating was halfway and asked him to check again it was 11 amperes....hmmm...as far as i knew the charging from the alternator with full load should not be less than 13 amperes slightly debatable but not less than 13 with ac on. got a used Japanese alternator had its amperes checked under full load. and poof the problem disappeared, never to return again. it so happens that the alternators commonly known as generators fitted in mehrans are so substandard that after running on full load for a few months, they stop working properly when they heat up. got the ac installed in the third one, had the same problem, all i did was to get a KABLI alternator and its running for ten years on ac with an engine clocking 180000 km consuming a quarter of oil every 500 kilometers...
