Flapping noise behind dash
 

For past 1,300 miles I've experienced a very annoying, intermittent rattling or flapping noise behind the radio/heating consol. It begins above 60 mph, occurs on smooth and rough roads, comes and goes, cannot be induced nor stopped. Sounds like a fan blade out of alignment or some plastic component vibrating against something else. It's at times loud and rising, at other times quietish. I've checked all Porsche and proprietary manuals for likely suspects in the area and cannot locate a likely culprit. I've banged, poked, tightened, and fiddled with stuff in the forward area and in the cab. All to no avail. Who's got the magic answer out there?

Fink
Denver

Well the fan is easy to diagnose if you just change the blower speed when it is doing it. If it increases or decreases with the speed of the blower, then you have found your issue. Sounds are awfully hard to diagnose without hearing them in person.

Believe me, I've fiddled with every fiddlable fixture in the vehicle. Opened and shut everything. Brightened and dimmed stuff. Turned it on and off and nothing impacts the random noise. Definitely not influenced by anything that man can wreak.

Finkmann der brennenden Wueste

What year is the car?

The flapping Boxster is a 2000 with 78K on it. Never made this noise before. Very frustrating. Bentley's Service Manual offers nary a hint as to what it could be. Tires all good, all plastic cowling up front tight, unchanged. Nothing new installed. YETSCH!

EUREKA! Flapping noise solved
 

Well guess what? It wasn't in the dash at all. How about the rubber moulding around the windshield? Got a Porsche tech guy to take a ride and he heard the noise overhead and felt around the top closing gear and felt vibration. Pulled over and sure enough about 30" of the moulding had been pulling free at speed and then flapping against the top of the window frame. Go figure. Currently very tastefully sealed down with duct tape and tomorrow the windshield replacement heinies get to do some magic under warranty.