As far as I know, the mist inside the windscreen is caused due to any one of the following reasons:-
1) Cold air from inside touches the hot windscreen
2) Hot air from inside touches the cold windscreen
In short, I think it is caused by temperature difference.
However, there is a front-defogger in Mehran. You can use it by rotating the knob-like button on the left side of the Speedometer box. I have read that you should also adjust the temperature to hot ( upto the end of the red line). I am not sure if it works without any heater/AC, but I adjust it anyways.
However, it is possible that the mist on the windows is caused by some lose fitting of the glass.
