I have a very peculiar problem with my Chevrolet Aveo. On driving at high speeds, (like 60-80kmph), the AC works fine, and the car is also not heated. But as soon as I slow down the car during heavy traffic, the car starts to heat up inconsistently, and the AC also renders itself ineffective.
I have got the coolant too, but this did not help. A mechanic told me that this is due to the slow speed of the radiator fan. As Aveo has just one fan, both for radiator and the AC, it has to move faster for a better cooling. When I drive fast, the radiator gets cooled by the air pressure, but this doesn't happen on slow speeds.
Is this a valid reason ?