Hello & Horn Question 79 GMC

[BeBeep]

Hello,

This is my first post; my name is Bob and I an in Fort Worth, TX. I just purchased a 1979 2wd SWB GMC Sierra Grande ½ ton and I am going to have a million questions for the board members.

The guy I bought it from misrepresented so many things about the truck, I have lost count. I now have to fix them one at a time and that leads me to my first question.

The horn does not work. The previous owner said it worked the “just day before but his nephews were honking it a lot and they may have blown the fuse”. Ok…..so I replaced the 20amp fuse and right away it blows. I put in a 25amp just to see and yes that blows too. I ran power directly to the horn and it works great so that is not the problem. I tried to find the horn relay but no luck; does anyone know where the heck that relay is?

I was thinking that the relay may be the problem but since I am no troubleshooting genius can anyone else jump in and give me some advice? I have a Chilton’s manual but the wire diagram does not even show the horn let alone a relay for it. I have also ordered some additional manuals but have not received them yet.

I appreciate any and all advice and guidance you can lend.

Thank You,
Bob

[Pyrotechnic]

It should be up on the fuse block underneath the dash on the drivers side. I can't pin point it exactly on the fuseblock for you but it is there. Hope some of this helps. The relay could be shorted out internally which could be why you're blowing fuses constantly. If a relay doesn't fix the problem, you might have a short somewhere in the horn wiring.

[bmartin9122]

Electric horns are essentially violent electric motors that heat up VERY FAST when used. They can be severely damaged and ruined by extended and/or repeated honking. In some cases, the horn can actually get stuck from overheating causing a short; this condition could explain your horn's problem.

The real trick in this case will be isolating which of the two tones is the culprit. Both tones are likely original, so you might consider replacing them both to ensure a powerful blast.

[BeBeep]

Thank you for the replies, I will follow both of them up and hopefully fix my problem.

Temporarily I wired up one of those horn buttons from Autozone and hooked it up to the horn so that I could pass the safety inspection but now I need to fix it right. Funny thing is I found one horn on the drivers side behind the grille but could not find a second horn. I will have to look again to be sure it has not been removed or moved to another location.

Thanks Again,
Bob

[bmartin9122]

You may find them hidden behind the headlight assembly.

[jermasaurus]

hey Nice lookin truck.

As far as the horn situation goes, it is probably more likely that you have a wiring issue rather than a relay or somthing blowing the fuse.

If you are using the same size fuse or smaller with your own switch you installed, then you know the horn is ok.

If you have an ohm meter, check if your wire supplying B+ to the horn is shorted to ground. I think it is a green wire- could be wrong


Good luck
-Jeremy

[BeBeep]

Thanks for the responses, I will be digging into it this weekend.

Bob