# Fixing Horn - How To



## cij911 (Oct 25, 2017)

The horn circuit on the GTO is rather simple, but I thought I would document how the horn circuit works, common problems, and diagnosing your specific issue.

The horn circuit is really just a relay (to the right side of the fuse connectors) , 12v + power to the relay, a switched power from the horn button / switch, and then switched power out from the relay to the horns.

If you are having problems with the horns, this is the order I would diagnose:
(1) Confirm horns work: apply 12v+ to the horn(s) directly and confirm whether they work. You can do this several ways, but the easiest is if you have two long wires with alligator clips - attach to the positive and negative of the battery and then the positive to the horn male plug and the negative to the body of the horn. If your horn works, then the problem is in your circuit. (Next step)

(2) Confirm switched power to horns: there are two easy ways to do this with the easiest being having the aid of a friend. Remove the plug from the horns, have a friend push the horn and while you measure voltage at the horn plugs (female). If you are getting switched 12v +, then the circuit is fine and if you verified the horns work, then you have a grounding issue with the horn and body of the car - clean horn grounding contact point or add a new ground wire from the body of the horn to the chassis. If you are not getting switched power, then you'll want to verify the relay is working. (Next step)

(3) Confirm relay is working : The horn relay sits on the firewall (engine side) to the right of the fuse box connectors. There should be three connected terminals - green wire (to horn switch), black wire (to horns), and 12v + (should be red and black). You will want to confirm the relay opens and closes by applying 12V + to the side where the green wire connects and grounding the side to the horns (black wire). I found the easiest way to do this was to unplug the relay and remove from the firewall and test on a work bench with a dedicated 12v source (eg. spare car battery). When you connect the ground and 12v+ you should hear the relay click - remove the power and re-apply to confirm opening and closing. If this works you will want to confirm continuity through the relay. To do this apply 12v+ to relay plug that went to the constant 12v+ (should have been a red and black wire) and will be below where the plug with the green and black wire connected. Then connect a voltmeter positive lead to the terminal on the relay that leads to the horns (black wire) and the negative voltmeter lead to the negative post of the battery (ground). Then use another another 12v+ (just take another wire connected to the battery) and tap the relay terminal that would lead to the horn switch (green wire) while watching the voltmeter - you should get ~12v. (If not your relay is likely dead.)

(4) Confirm power to horn switch: This is hardest and most time consuming part of the diagnosis and frankly I found little online with regards to the circuitry or how the mechanism actually is supposed to work. It is rather simple and with a little patience, rather easy to repair. Essentially there is 12v coming up through the switch that grounds out on the steering shaft when the button is pushed (sending switched power back to the relay - green wire).

The first thing you will need to do is remove the horn button / pontiac logo cap - use a special tool or a 90 degree pick to pop off the center cap and expose the wheel nut (3/4"). Remove the 3/4" nut and remove the horn ring (chrome trim). You will now see a little spring loaded metal post at about the 10 o'clock position - this essentially grounds the horn via the steering column when the horn switch is pushed in. Remove the steering wheel using a wheel extractor (the steering wheel is pressed on and you will need to use the proper tool otherwise will damage either the wheel, the column, or both). Once the wheel is off you will see what I call the horn collar. Mine was filthy and using the voltmeter I would get intermittent connectivity. I would recommend pulling the collar off and cleaning all contact points with electrical contact cleaner (I use CRC electronic cleaner) and a lint free cloth. Touching the spring loaded tab and the bottom side of the collar, you should get solid electrical connectivity - use a voltmeter to confirm. With the collar off, you should have clear access to the turn switch and at about 5 o'clock you should have another spring loaded tab that should be hot 12v+ and this connects to the relay via the green wire. While the wheel is off, this is a good time to clean the turn signal switch with electrical connector cleaner as well. (I put a rag underneath the switch and sprayed liberally while moving the switch.) In my case the collar was a problem area and was rectified after a good cleaning.

You should be back to having a nice working horn. Enjoy and safe driving


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## Goat Roper (Oct 28, 2014)

I might add to the first step if the horns don't work tap on them with a small ball peen hammer.
Mine didn't work and I removed them and got them to work jumping them on the bench after tapping on them.
There is also a set screw on them you can turn to tune them, one is a high tone and one is a low tone.
The diaphragms get stuck from non use, once you break them loose blow them out with compressed air and tune with the screw.


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## Js1969 (Jun 11, 2017)

I need to mess with mine some more as I added the 1970 GTO formula wheel on my 69 and for some reason it’s not working correctly. It worked as I tested it through the install but once complete the horn button isn’t reaching/making contact with the correct area.


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## cij911 (Oct 25, 2017)

Js1969 said:


> I need to mess with mine some more as I added the 1970 GTO formula wheel on my 69 and for some reason it’s not working correctly. It worked as I tested it through the install but once complete the horn button isn’t reaching/making contact with the correct area.


It sounds like your button is not properly grounding the circuit. I'll add more explanation how this works later today.


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## Js1969 (Jun 11, 2017)

cij911 said:


> It sounds like your button is not properly grounding the circuit. I'll add more explanation how this works later today.


Yeah, I can make it honk without the horn button/ cover on, but once it's all installed, nothing.


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## cij911 (Oct 25, 2017)

Js1969 said:


> Yeah, I can make it honk without the horn button/ cover on, but once it's all installed, nothing.


So that means the button is interfering with the grounding of the switch. Can you post a picture of the button and the wheel without the button ?


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## Js1969 (Jun 11, 2017)

cij911 said:


> Js1969 said:
> 
> 
> > Yeah, I can make it honk without the horn button/ cover on, but once it's all installed, nothing.
> ...


I can’t at this time since the GTO is in the shop getting some body work fixed. When I do get it back I’ll be sure and post a picture.


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## IceBolt (Jul 28, 2020)

@cij911 - thanks for the useful info! Got mine working.....rusty terminals on horns. Still trying to find the actual horn relay....is that picture above looking at the firewall, driver side?


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## ted_1776 (8 mo ago)

cij911 said:


> The horn circuit on the GTO is rather simple, but I thought I would document how the horn circuit works, common problems, and diagnosing your specific issue.
> 
> The horn circuit is really just a relay (to the right side of the fuse connectors) , 12v + power to the relay, a switched power from the horn button / switch, and then switched power out from the relay to the horns.
> 
> ...


Thank you for the horn fix. Great info!


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