An easier way to do that is to just short the terminal that's not hot to ground (bypassing the horn button and the need for a second person.) If the horn works then, the problem is likely at the horn button. Problem with doing it that way is "which terminal is not hot". Both should be hot until the horn button is pushed.
'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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