12/09/22: Unfortunately, my plan fell apart when I tested the install. Only the high toned horn worked. The low didn’t even make a click. I was baffled. I retested each horn separately on 12 volts and both worked, loud but did work. I tried adjusting the low toned horn while in series but to no avail. I tried feeding the low first then the high (opposite to the way it was), again no joy.
The reason only one horn worked is because that high tone horn's electromagnet pulls its diaphram (the noise maker) and opens its switch before the low tone horn's electromagnet pulls its switch open. This happens because the hi-tone is designed to operate at a faster rate (higher tone). When either switch opens in your series circuit the spring in each horn will be pushing the diaphram back to its "at rest" position to close the switch and start the dance over again.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
