A Class little fan in rooflight

[contheosius]

Shortly after I replaced my radio for a MP3 player I noticed an irritating sound coming from the roof light. I actually thought it could be tweeters going wrong and took the car back to the company who fitted the radio.

They were also baffled and opened up the roof light. To our amazement there were no miniature speakers in there. But a little black box with a tiny little fan.

The sound it makes is most irritating. What is the purpose of the little fan please?

 

[davidsl500]

Its the sensor assembly for the Climate Control/Air Con - the fan sucks air in over the sensor to determine cabin temperature.

 

[jberks]

called the "Ambient temperature fan" I believe.
MB replaced the one in my C as I could hear it. It should be silent.