Horn Wiring
 

Hey there, got an 87 s4 N/A. Need a horn to pass VA state inspection. I found the horn and it works when I ground it out, but I think the horn buttons don't work. THe ones on the steering wheel anyways. I had seen in a wiring diagram that the horn relay is in the computer. Just wondering if I swap the computer, if I might get the horn to work. Or is it possibe to rewire it?

Is it legal to have the horn running on an auxiliary switch? If so, you can get relays and push button switches at Radio Shack for dirt cheap. Just wire it up yourself...

From what I understand is the soldering connection in the ECU for the horn is frequently the cause of horn failure. Try the above suggestion if you just absolutely need it to pass. You can worry about the horn later. Until then, just use your headlights to warn people in front of you to get out of your way instead of the horn.

Im having a similar issue. Ive checked the cpu and the relay in there. I've also checked the horns and they work direct. I can ground the button to no avail. BUT if i ground direct to the plug the horns work. WTF??? Can a busted solder not make enough ground at the steering wheel to set the horns off; but a direct ground (power probe) set it off? Or do I have a short some where after the steering wheel and before the plug?

C.....P.....U

Just get a piece of wire bare on both ends. Put one end in the the CPU plug where the horn signal from the steering wheel is. It's a green/orange wire.

Put the other end of the wire to a known gnd point. Horn should honk if the fuse is good. Leave all plugs connected, just do the backprobe of the horn wire at the CPU plug.

Shoulda honked if the relay in the CPU is good AND the power from the fuse to the relay is good.

Horn did not honk? Pull the plug off the CPU and jumper the green/red to the green/white. Horn should honk if the fuse is good.

Most early series four non honks come from a bad/cold solder joint at the plug or rather jack on the CPU. Try wiggling the wires at the plug and press to honk.

The STOP fuse powers it. If you have stop lights, the fuse is good.

I installed an external relay for the horn to by pass the bad relay on my CPU. I used the horn switch at the steering wheel to trigger the negative side (coil side) of the relay.