<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rodster:
But I am curious what you mean by popping A/C vents? </div></BLOCKQUOTE>

Heating and cooling my truck generates quite a bit of popping sounds while driving (I guess from expansion and contraction) during the more extreme temperatures (hot or cold). My guess is either the cheap plastic of the dash or maybe even the ducts themselves. I've had two '05's that have both behaved this way, so I don't think it's just a quirk.