Automatic backlight adjustment not working

Hello,

My 2012 13inch MBA is from this July, and I never got the automatic backlight of the keyboard to work.

I can manually turn on/off the backlit keyboard, but the automatic setting doesn't do anything.

Even in a pitch black room, the keyboard won't light up.

My 2007 Macbook Pro had this feature working like a charm, so I wonder why it doesn't work on my new machine.

The MBA is running Mountain Lion with the last 10.8.2 update.

Any idea guys?