Horn and horn relay

PILOTBILL

MEMBER
1983 GMC S15
2.8L
V6
2WD
AUTOMATIC
142,533 MILES

Hello, I have been working on the horn and horn relay for a couple of days now. I now believe, I might have found the problem. Every time I push on the horn, the pickup blows the horn fuse in the fuse box. I think that there is a short in the steering column some where. I have removed the steering wheel cover and have disconnected the horn wire. Since I don’t have a steering wheel puller, do you think that a horn button kit would work for me. It would save me a lot of work. I only have two (2) weeks left to get my horn to work so that it would pass the State Inspection here in Texas. I have installed horn button kits in other cars that I have owned in the past.

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

Hold on. Since you didn't list any tests you've done, lets look at the most likely suspect first. That is one of the horns is shorted. The only thing the wiring in the steering column does is ground the horn relay through the horn switch to turn it on. If that wire was shorted to ground, the horn would blow all the time.

The first thing to do is unplug both horns, install a new fuse, then listen if the horn relay clicks when you press the horn button. On the slim chance the fuse still blows, I have a trick that will prevent you from wasting more fuses while allowing you to work in the circuit to find the short.

I tried to post the wiring diagram, but once I finally found the elusive horn circuit, the diagram is unusable even when blown up 500 percent. You're going to have to rely on my memory instead. If the relay clicks now when you press the switch, one of the horns is shorted, which is fairly common. You can replace both or you can connect just one original horn and see if the fuse blows. If it does not blow the fuse, you're going to have a sick-sounding high-note or low-note horn by itself.

There's no point in trying to figure out which horn is shorted with an ohm meter because while the shorted one will read 0 ohms, the good one will too. When current flows through the horn's internal coil, it sets up a magnetic field that pulls a metal diaphragm, and that opens a contact that turns the horn off. The diaphragm relaxes, and that turns the contact on again and the process repeats as long as you hold the switch. The ohm meter can't provide enough current to make the diaphragm move, so the contact never gets pulled open. That's why you'll be measuring through the coil and it's going to read 0 ohms even though the horn is okay.