I'm new to this site and the world of Boxster ownership so firstly hello!
I've just replaced the standard stereo with a pioneer bluetooth, telephone/ipod unit. Since doing that the horn beeps once every time I set the alarm - Any idea what I have done!!?
Or you can disconnect the lead that's attached to the trim piece that makes the horn beep. It's a black wire behind the wiper knob that's just attached to the horseshoe.
What pioneer unit did you get? I put in an AVIC-D3 a few months back.