I've recently acquired an 86 toy 4x4 p/u. The previous owner (or someone) replaced the stock horns with Hella horns. However, at this time...none works. I've searched under the hood and found the wires from the horns that go to a small aftermarket relay. In addition to the wire from the horns, there are others that go to the + side of the battery and two others that tap into the truck's wiring harness. These two wires are green with red stripe and green with white stripe. I have tested the horns by applying 12v to the wire that goes to the horns...they work. I have tested the horn button on the steering wheel by assuring it has continuity with ground...it does. However, I cannot find continuity from the horn button to either of the two green wires.
12-16-2010, 07:20 PM
Does the relay have four prongs? If so, one goes to +12V, one goes to ground, one goes to the horn, and one is an input trigger pulse (Should read +V then you press your horn). If all those are getting the right signals, check your ground and replace the relay....
Good Luck !!!!
12-17-2010, 10:15 AM
Thanks... yes the relay does have four prongs and I've hooked them up as you described. I think my problem is that I'm not getting connection to the horn button....and, as I look at it, the horn button provides a ground...not 12v....I think... as the wire coming out of the steering column is connected to a ground plate in the button assembly. I have verified continuity between the button's ground plate and chassis ground so I know the button is ok.
As I mentioned , I have two wires from the truck's harness that the previous owner connected to the relay. One is green/white and it has 12v on it from a 15 amp fuse. The other is green/red and is an open wire as it has no continuity with either ground or 12v. I've connected that wire to ground and then ran my ohm meter between it and the horn button and when the button is pressed, there's still no continuity. I've connected it to 12v and ran my volt meter to the horn button and no reading of 12v is there.
I will try replacing the relay with a new one and see if that makes a difference.
Thank you so much for your help...I really appreciate it.
12-17-2010, 04:12 PM
Ok... finally figured it out. The relay and wiring were fine. The tip off (after it eventually soaked through) was that I wasn't getting any continuity between the horn button and the signal wire that went to the relay. Turns out the horn contact pin on the steering column that makes contact with the horn button brass ring was worn down (truck is 25 years old and has 247,000 miles on it) to the point to where it was no longer touching the ring.
Now I just gotta figure out how to replace that pin......
thanks again for your help.
12-18-2010, 07:46 PM
Glad it all worked out -- electrical gremlins are always frustrating to troubleshoot....
12-20-2010, 10:26 AM
Cheapest way is probably git a used steering wheel... ;)
And put some graphite back there now and then... ;)