dash noise

[cavx5]

hi everyone...i recently posted a thread about a minor noise coming from either underneath the drivers side footwell or behind the instrument cluster i quite cant pinpoint the exact location..the sound occurs every 25 seconds and lasts 1 second..it only occurs when the hvac system is off and it sounds like a vent door is either trying to close or open or a temperature sensor making noise....i feel embaraased taking it to the dealer for this..they will definetly think i am crazy...2005 x5 4.4 with 17k...what do you think...thanks rob