I bought a used 1999 komatsu pc200lc6, 4200 hours, great shape. Anyway, the horn does not work. I first check the fuse, fuse is good. I take the two horns off and test them, they make some noise (they were in terrible shape), so I buy new ones and slap them on, no noise. I disassemble joystick, looks good, everything seems to be in good shape. I pull out my test light and check the connectors, no power coming from wires. I check the fuse box and theres power for the horn 'slot', anyone have any ideas or suggestions. :Banghead
Work from the powered fuse and follow the wires. It's a pain staking process but it's what we do at the dealership. Nobody likes an electrical nightmare- I feel your pain. Another point is that it's probably as simple as your positive being grounded somewhere -so look for breaks or deterioration where the wire could be grounding out. Good luck.
The right way to fix it is to pull the fuse panel and see what's going. The fast way to fix it is to make a jumper to get power over to the supply side of the fuse. Good luck with it.