Horns not working. Anyone have the diagram?

Electronic systems, stereo and Holden iQ, wiring, it all goes here....
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91C02920
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Joined: Mon Nov 02, 2015 7:19 pm

Horns not working. Anyone have the diagram?

Post by 91C02920 » Mon Nov 30, 2015 8:36 pm

The horns in my car are not working when I press on the steering wheel (or at all for that matter). Does anyone have the wiring diagram for the horn circuit under the hood after the fuse box?
Right behind the grille I have two cut wiring looms. On the passenger side it has 4 wires - green, blue, orange and grey. On the drivers side there is a cut, I can't tell the colors yet, need to strip them down, and at work still. Something was removed here. I'm kind of wondering if that wire ran from one horn to the other. The diagram would be a help.

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The Tech
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Re: Horns not working. Anyone have the diagram?

Post by The Tech » Tue Dec 01, 2015 12:35 am

Try here. This is what I used.

https://www.gmupfitter.com/files/media/ ... Manual.pdf" onclick="window.open(this.href);return false;
2011 Alto Gray Caprice PPV 9C3, Kooks Long Tube Headers, Kooks Drag Cats and Crossover, Solo Axle Back System.
1996 DGGM Impala SS
1995 Caprice 9C1 red over white
2015 Bright Yellow Jeep Wrangler, the better half's car.
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9C1fanatic
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Location: Texas Hill Country

Re: Horns not working. Anyone have the diagram?

Post by 9C1fanatic » Tue Dec 01, 2015 2:02 am

The 4 wire loom under the hood you speak of is the factory installed grill lights/siren speaker circuit. Its just a factory run circuit so upfitters don't have to punch holes in the firewall to run wires up there for those items. It wont affect your horn.

What you need to look at first is the horn circuit (relay) wiring in the upfitter harness. This circuit is opened on purpose during upfitting to allow for siren activation using the vehicle's horn ring on the steering wheel. When the car is taken out of service sometimes they don't reconnect the circuit so it remains open causing the horn to not work. That is most common issue for no horn. Check the link in the previous post to get a wiring diagram or color.
Garner Ames



1975 Pontiac Grand Am L77 - 14.82 @ 92.89
1991 Chevrolet C1500 L31 Vortec/5 Speed
2014 Chevrolet Caprice 9C1 L77 - 13.60 @ 105.87
SS Roto-Fab CAI, Solo axle backs

2015 Chevrolet Caprice 9C1 6.0L (owned by the tax payer in all of us)

Solo axle backs

91C02920
Posts: 122
Joined: Mon Nov 02, 2015 7:19 pm

Re: Horns not working. Anyone have the diagram?

Post by 91C02920 » Tue Dec 01, 2015 6:08 pm

Thanks to all!
That was easy :)
I found the 2 brown/black under the dash both ends were connected to black wires running to the right kick panel.
The brown/black both appeared to have female ends (it was early, will look at them again later), so I cut the two black wires coming off of them and twisted them together and electrical taped them.
Now the horn works! :)
This is just to get past state inspection today. I'll trace the blacks from where I cut them and take them out later. Also concerning was the large red/white wire that was cut under the dash. I'll have to take care of that one for sure.

Should those brown/black wires have had a male/male connector or anything between them?

9C1fanatic
Posts: 418
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Location: Texas Hill Country

Re: Horns not working. Anyone have the diagram?

Post by 9C1fanatic » Tue Dec 01, 2015 9:57 pm

The two female connectors are most likely how they interrupted the circuit and connected it to the siren amplifier. Connect it back however you see fit.
Garner Ames



1975 Pontiac Grand Am L77 - 14.82 @ 92.89
1991 Chevrolet C1500 L31 Vortec/5 Speed
2014 Chevrolet Caprice 9C1 L77 - 13.60 @ 105.87
SS Roto-Fab CAI, Solo axle backs

2015 Chevrolet Caprice 9C1 6.0L (owned by the tax payer in all of us)

Solo axle backs

white9C1
Posts: 1
Joined: Fri Oct 26, 2018 1:44 am

Re: Horns not working. Anyone have the diagram?

Post by white9C1 » Tue Oct 30, 2018 12:43 am

I had the same issue with no horn working. I found a brown and black wire 18g under the passenger side dash in the wiring harness that leads to the blower motor. It looks like a service loop and it was cut. Spliced the wire back together and my horn is working again. Hope this helps.

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