I was just listening to this week’s podcast (8/28/10 show) and was yelling “no no no!” at what the brothers were saying; especially when they talked about pulling on the wiring harness.
A honking horn while braking is a well-known issue for both Boxsters and 911s of that era. The airbag support frame has rubber grommets that get old and sag, and cause the horn to honk at the slightest shift–bumps or braking. It happened to me in my '99 Boxster too and it is indeed embarrassing. Like I’d pull up on someone, brake to slow down and the horn would honk at them - Doh!
The fix is super-easy:
Short term, fold a business card a couple times and stuff it in the lip at the top of your airbag to wedge it out. Seriously. It stops it.
Do this while you wait for your new airbag bracket to come (or while you drive to pick one up at the dealer). I got mine online for about 70 bucks and replaced it literally in about 20 minutes.
I posted the info in the Boxster wiki (that’s my steering wheel showing where to put the card; link to detailed instructions there):
http://box…n_Problems
Basically you remove the airbag with a torx wrench, unplug a ground wire, unscrew the bolts holding the bracket and put the new one on in its place and put the bag back on. It’s really that easy.
I realize Cartalk probably wants to keep its audience, but for more depth in Boxster repairs, tips and tricks, check the above Wiki and also check the website called Porsche Pete’s Boxster Board.