Hello & Horn Question 79 GMC - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BeBeep · 03-26-2007, 05:45 PM

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 · 03-26-2007, 06:35 PM

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 · 03-26-2007, 10:50 PM

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 · 03-27-2007, 06:35 AM

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 · 03-27-2007, 12:37 PM

You may find them hidden behind the headlight assembly.

jermasaurus · 03-27-2007, 09:14 PM

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 · 03-29-2007, 04:46 PM

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

Bob

03-26-2007, 05:45 PM	#1
BeBeep Registered User Join Date: Mar 2007 Location: Ft. Worth, TX Posts: 20	Hello & Horn Question 79 GMC 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 Attached Images

03-26-2007, 06:35 PM	#2
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: Hello & Horn Question 79 GMC 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.

03-26-2007, 10:50 PM	#3
bmartin9122 Registered User Join Date: Jan 2006 Location: Texas Coastal Bend Posts: 169	Re: Hello & Horn Question 79 GMC 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. __________________ 79 GMC Sierra Grande K15 --PPG paint code 62608 Sunburst Orange Metallic (WA802K) --Gentex auto-dimming rearview mirror model K31 --Carriage Works billet grille model 40071 --Go Industries 2.5" tubular stainless headache rack --Sylvania Silverstar sealed headlights model H6024ST --Texas Saddlebags center console model 101 --Brown's Welding class IV V-5 pipe bumper --Ramsey RE8000 winch --33" tires Last edited by bmartin9122; 03-26-2007 at 10:51 PM.

03-27-2007, 06:35 AM	#4
BeBeep Registered User Join Date: Mar 2007 Location: Ft. Worth, TX Posts: 20	Re: Hello & Horn Question 79 GMC 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

03-27-2007, 12:37 PM	#5
bmartin9122 Registered User Join Date: Jan 2006 Location: Texas Coastal Bend Posts: 169	Re: Hello & Horn Question 79 GMC You may find them hidden behind the headlight assembly. __________________ 79 GMC Sierra Grande K15 --PPG paint code 62608 Sunburst Orange Metallic (WA802K) --Gentex auto-dimming rearview mirror model K31 --Carriage Works billet grille model 40071 --Go Industries 2.5" tubular stainless headache rack --Sylvania Silverstar sealed headlights model H6024ST --Texas Saddlebags center console model 101 --Brown's Welding class IV V-5 pipe bumper --Ramsey RE8000 winch --33" tires

03-27-2007, 09:14 PM	#6
jermasaurus Registered User Join Date: Dec 2004 Location: New Lenox, IL Posts: 442	Re: Hello & Horn Question 79 GMC 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 __________________ 79 Jimmy slammed AKA James Down

03-29-2007, 04:46 PM	#7
BeBeep Registered User Join Date: Mar 2007 Location: Ft. Worth, TX Posts: 20	Re: Hello & Horn Question 79 GMC Thanks for the responses, I will be digging into it this weekend. Bob



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