Hi all. My horn gave up the other day. I'v tested it directly on the battery and it works fine, checked the fuse and checked the windshield wipers that share the same fuse - everything OK. Now, from what I can understand out of the schematics I found here the yellow cable always has + 12 volts while the black -/ground is cut until one hits the button on the steering wheel. The odd thing is:

1. The yellow wire has a potential over ground of 1 V at the maximum (key in return position)
2. The black wire is short circuit to the chassis regardless of if the button is pressed or not

What happend here?

Since the windshield wipers and horn share the same + supply I suppose there's a split point somewhere after the fuse. Maybe something happend there. Does anyone know where this split point is located? And why does the black wire connnect to ground all the time?

The horns are grounded, when you depress the switch this supplies 12volts to activate the horns. You have tested the horns and they are good. Test the switches next, make sure they are getting power. This will help to narrow down where to look next.

I checked with my mechanic today, he confirmed that you ground the - cable by depressing the buttons. The yellow + wire is supposed to have 12 V all the time.

Then your test results imply that not only do you have a break in the horn 12volt wire, but also your horn switches are bad. Even if you re-energized the power wire the horns would turn on and not shut off till power was disconnected.

Correct, but I also checked the - cable while disconnecting the slip ring by the steering wheel. Still connects to ground.