[kevinbell]

I always noticed a very slight hum when I entered the car, it turns out there's a very small fan behind the three slots in ACC module, I can see the thermocouple mounted to the middle slot, I assume the fan is "sampling" the cabin air to get an accurate temperature reading. Never had a car with a fan to sample cabin temperature - pretty cool, at least the hum doesn't bug me anymore since I know what it is. If you put your finger over the three slots you can hear the pitch of the fan change.<P>

 

[TurboJet]

I had a 88 Saab Turbo with ACC that had the same arrangement... a thermocouple with a little fan to draw cabin air past it.<P>You could see the fan turn if you lit it with a flashlight but I could never hear it.<P>Not a cheap part to replace should it ever go bad, BTW. I didn't have to... had a connector get a bit corroded and once cleaned it worked fine again.<P>