Pushing horn button applies 6v across the 2 wires. Stock horn wiring would have -6v going to one terminal on the horn at all times. The other terminal would also measure -6v until the horn button was pushed which would ground this terminal letting current flow through the horn and causing noise.
'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.
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