I have a 2002 s80 and when I shut it off I can hear something in the dash running. It has killed the battery numerous times and I just replaced the battery. It kind of sounds like a little fan running behind the radio. Thank you for the help in advance.

 

Well, there is a small fan attached to the back of the radio which pulls the air in for the temperature control (I believe), you can see the small vent on the front of the radio. On my S80 it tends to start running when I unlock the car, and then turn off after I lock the car. But eve if it did stay on all night, I would be suprised if it was enough to drain a good car battery.

Stu

 

I actually noticed this noise before and wondered what it was.. I also wondered if its as loud in all cars as it is in mine....

A really nice feature of the car is that the air fan runs to keep the car cool when your not in it.. I'm not sure how long it does this for without timing out but it really helps to cool the car.

 

The fan behind the radio is tiny, about an inch diameter, the one which keeps blowing air to stop mould, etc is alot bigger but yeah, its a nice feature.

Stu

 

Yea I know they are two distinct fans... I can tell the difference, I just figured out the purpose of the larger one...
the small one, im not entirely sure about
I always wonder why the small one is pulling air for temp control when the car isnt even on..

 

That sensor is the inside temp sensor which helps the computer read the inside temp. When in auto that is what the computer uses to see the inside temp so it can adjust to what it needs to.