[bergie]

Jseery's reply with wiring diagram was great. I was not familiar with this era of horns. The fact that these horn bodies are insulated from ground would seem to make it even simpler to put in series. According to the diagram, the yellow wire supplies 6 volts to each horn in parallel. The BLY (blue-yellow tracer) wire supplies ground to each horn in parallel from the horn button via the lighting switch. Why couldn't a person keep the yellow wire (now supplying 12 volts) to one of the horns (coil wire) and the other terminal of the first horn should now be wired to the coil terminal of the second horn. The BLY(blue-yellow tracer) wire on the second horn remains connected to the horn button via the lighting switch. Now the horns are wired in series and should sound the same as when using six volts.