My horn quit working quite a while back. I recently bought a Grant steering wheel and decided to get my horn working again. I looked up the wiring diagram, but can't seem to figure out where the heck is the relay ! I did notice that one horn is shot while the other is working.
Questions:
1) Where in world is the relay? Or is a 1979 suppose to have a relay? No cruise control in my truck.
2) I took the green wire off the horn and with ignition on, tested to see if there is any voltage in there - nada - does it mean that the wire is broke somewhere? Chilton also shows a fuseable link in the diagram, but cannot find where in world that is either.

Any help will be appreciated.

 

Have you checked you're fuse's?

 

Good question ! I cannot seem to find a fuse for the horn either ! I looked in the fuse box diagram in the owner's manual.

 

Wiring diagram in the parts book illustration shows the horn relay to be mounted on the firewall above where the main wiring loom comes into the interior.

The picture isn't clear on whether the relay is outside under the hood or inside the interior above the steering column. The relay is a small rectangular box, originally the color of burnished metal

 

For some reason 78/79's without CC didn't have horn relay's.

Mine didn't


The circuit is part of the main wiring and comes directly from the horn pad to the horn.....no fuse.

The fusible link is about 18" from the starter relay connection.

Undo the wrapping.


Perhaps the horns are seized ?

Try tapping them or applying power to them from the battery post.

 

Million1, I applied power from battery and found one works the other don't. But on the green wire that comes to the horn does not have any juice. I stuck the red tip of my multimeter in there while grounded the other tip right to the negative of the battery. Ignition key is on. So, it tells me that somewhere the connection is lost.

 

Dennis, you are as right as rain...the book sez: D6TZ-13853-A Horn Relay...use with Speed Control. There is no other horn relay listed for 1978/79.

The pic in the illustration in the parts book shows the horn relay "married" to the Speed Control Amplifier. I never looked at the application till now.

 

That's because the NON- cruise horn power in the turn signal switch is used by the Cruise control and the special horn harness for w/Cruise vehcles is used to power the horn circuit.

But in this instance he has a green wire where the NON-relay wire should be Blue/yellow stripe directly to the horn

 

The wire is kind of dirty - but I can say for sure it is green. Doesn't look blue or yellow.

 

You have factory dual pitch horns right?


According to the wiring diagrams this is how dual horns were wired for 1978/1979...


Circut 460: Yellow wire comes off the headlamp switch and goes to the Horn pad switch.

(It seems silly to me for the horn to be connected to the headlamp switch and to get its power from the headlamp power feed, but the diagram says it in black and white...)

Circut 1: Blue/Yellow stripe wire from the horn pad switch goes to connector 302, where the color of the wire is changed to yellow/green stripe.

The yellow/green stripe wire from connector 302 goes to the low pitch horn, splits off at the low pitch horn connector #303, and a second yellow/green stripe wire goes to the high pitch horn.

============

Why the horn wires change colors at connector #302, is it uses the older horn harness extention that they used from 1973 to 1977 for dual horns, and the color for the horn circut on the 1973-1977 was yellow/green stripe after the horn relay.

So if you follow the yellow/green stripe wire from the horns back it should turn to Blue/yellow stripe at the first connector you come to.

hope this helps...

 

I think I will have to take the dash off or get the vents off to trace the wire. I will let you know what I find.

 

Hold off pulling the dash...I doubt it will do any good...as the wire leaves the headlamp switch and goes to the horn switch..that means it runs up inside the steering column.

Make sure to remove battery cable!!!

 

Your column connector should look like this.