right, can anyone kindly tell me that, how can I test whether the duo value, or the temperature control of the ventilation system fail or not??

The reason I need help, because during the traffic jam in the sunny day, the air vent in the driver side will become very hot, just like you have turn on the heater,(just the driver side) but the setting is 18 degree C!!!

after we drive for about 3 min, the air vent cool down again. Is that high temperature come from the engine??


P.S: I don't have an air-condition in my 300E, as I am in UK.