this is a weird question coz it's actually about a "noise/sound" that i thought was normal upon start up during the first few months of my ownership of the rdx.

lately though i have NOT been hearing this sound -- it sounds like a "moving machine/vacuum" just prior to my switching the ignition key before the engine starts. it's like a whirring sound but goes away.

i first thought this was normal as i didnt have any problems in the past, now i cant hear it. do you guys have any idea what this is? some people state it's the brake vacuum pump, others say it's got to do with the climate control system. either way, is this an issue that needs to be "fixed"? (eg. is the sound supposed to be there or not?).

ps. the best way that i can describe the sound really are:
a) it's like something is moving into position upon start up - some lever maybe
b) it's like a whirring sound (definitely NOT the turbo as the engine hasnt even started yet at that time)
c) it goes off in 2-3 seconds all the time - im not yet even out of the garage the sound already stops
d) lately i dont seem to be able to hear it anymore (but it's been colder these days)
e) it seems to be happening only when i start it up in the mornings (not when im already out during the day -- at least ive never heard it -- it's a faint sound -- and it's normally the most quiet when i start up in the garage in the mornings relative to where i start the car during the middle of the day {eg. outside in a busy parking lot, etc})

thank you for your input

its the climate control flaps. Mine does it and occasionally does it while idling as well...

thanks mau, does this need to be "Fixed"? nothing's wrong really but what's the prognosis on this - a defect? or normal?

(eg. as "normal" as rattling 1/8th open windows which i didnt bother fixing after reading that this is an inherent honda problem)

I've always known the whirring sound on Hondas that occurs when you turn the key to the "ON" position but haven't actually turned to start the engine yet as the fuel pump pressurizing the system. I used to hear it all the time on my Accord...haven't heard it (or listened for it) on the RDX though.

I one that sounds like an electrical buzz under the dash when I turn the key before it starts.

ok so this thing is normal then, with or without the sound, it seems... and yes, it does sound like an electrical buzz and im quite sure everyone that posted here is hearing the same thing.