Thanks for the replies. I actually fixed it. I grounded the steering column to the dash and managed to get a crackling sound out of the horn. After cleaning all connections, a bit better but still nothing. I haven't run the truck for a year so the battery was still not fully charged. Decided to pack it in for the night and started the truck up to let it run a bit and tried the horn one last time. Yeah, apparently horns needs a full 12 volts to work, at least this one...