bick51

Just finished installing air horns on my 2016 Cayenne. Did not want to break into the factory wiring, so I made a pigtail from a salvage yard donor horn and wiring connector, with a tap off the 12+ volt wire.
For those interested, the wiring connector to the stock horn is a standard VW/Audi/Porsche part 4D0971992, available on the internet. What I could not find was the receiving 'male' plug on the horn, hence the use of a donor horn from an Audi A4.


The wiring diagram with the air horns wanted me to tap into the ground wire of the horns (brown), which assumes that the horn ring completes the ground circuit like a 1950's 365.
Not wanting to screw with the CANBUS wiring of the Cayenne, I opted to tap off the 12+ volt wire to the horn, using the driver's side horn. The tap is the yellow wire above on the new pigtail. All the connections were potted in epoxy.
I also opted to run a separate ground wire for the air horn compressor back up to the factory ground by the firewall. The new 'harness' was then wired as follows:

The tie-in points for power and ground are up under the driver's side plastic along the fender. For a 30 amp fuse and nice grommets, I sacrificed the end of a 'Battery Tender' lead, available for peanuts. The wiring was then enclosed in a black split wire loom, just like factory.
This can be had at Lowes (of all places) with 10' of 3/8" for under $3.
The compressor and trumpets were then mounted on a common piece of galvanized steel, and bolted down to the same bolt used for the driver's side horn. The final installation is shown here.