Agreed, you just have to either disconnect the wire to find the "input" hot one or trace them. You can still be working alone to do that. Agreed and a good idea. By the way, I have a '51 (not '50, but I'd bet they would be the same) GMC Maintenance manual that has about a page of how to adjust and troubleshoot the horn. If you are interested Mike, I'll post it or send it to your e-mail. Current draw at 6 volts is spec'd at 9 amps and horn frequency is 302 cycles per second.
'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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