Question about when the Auxillary Fan turns on

[Sepehr]

Is the Auxillary Fan supposed to automatically turn on whenever the Air Conditioning is on? I notice that all of the newer Mercedes-Benz cars automatically turn it on whenever the AC is running. I know that my Auxillary fan works because when I unplugged the wires for the Climate control unit ,the fan turns on.

[DynoXG]

Mine usually come on when the ac is on intermittently, especially when the car is stopped.

[Sepehr]

hmm...for some reason my Auxillary fan doesn't turn on intermittenly. Does anyone have any suggestions to a solution? Could it be a faulty Climate control unit?

[First Benz]

Are you sure they aren't coming on?

Normal operation is directed toward the A/C system. But only when the pressures in the system get high enough, then the fans switch on and pressures drop.

The reason they come on more in hot weather is because pressures run much higher in the summer time, not to mention the A/C is on much more. :)

Are you sure the A/C system is functioning properly?

The second use for the fans is a fail safe for the engine temp. If engine temp gets close enough to the red, [somwhere around 280-300] they will turn on in a last attempt to cool the motor down. However, this will never come into play as long as your cooling system is functioning properly.

I would take a look at the fuses, and if they are good, don't worry about it too much. My fans hardly ever turn on.

Eric

[Sepehr]

Thank you Eric. I think that you're right. I thought that there was something wrong because the w203 C class that my sister owns automatically runs the Aux Fan as soon as the AC systme is turned on.

I learned that my w202 car only turns it on (as you suggested) after a long while or at high temperatures. Thanks for the info.