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rabit replied to Andre Kristian's topic in 996 Series (Carrera, Carrera 4, Carrera 4S, Targa)Hi, hope you already found the replacement part; however, if you kept the gear, please take some measurements, inner and outer diameters, bearing size, number of teeth on gear etc. These are--more often than not--standard parts that OEM manufactures source out of a catalogue. I'd be happy tp do a bit of research, and report back; might be helpful for the next person that runs into this.
I'm aware this is an old thread and the OP has long resolved the issue... For reference, the reason the horn hums is that the system is continuously applying a small amount of current and monitoring to see that it is present. If you arm your car, and then unplug the horn, you will see that the flashers will immediately come on. The normal current draw, when all interior, exterior lights, as well as odometer illumination is off, and doors are closed, is ~50 mA (i.e., 0.05 A).