What are the chances of both horns failing. I would suspect loose/broken wires or grounding. Most likely grounding since as things corrode the ground is typically compromised.
I find the horn is not distinctive or suited to Porsche, just plain boring really so perhaps you have a good excuse to upgrade.
Something more European sounding perhaps.
Anyone heard a good horn lately.
Old style higher pitched dual trumpets perhaps.
Personally for a noisy warning device I like the guns switch myself
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"It broke because it wants to be Upgraded

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2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)