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Horn not working

Hi,
After months working on this car I have only one thing left before i can take it for safety.
The horn.

It will not pass safety without it.
When i press the button i hear faint sound and the green light on the dash lights up for a second (my 8 year old son noticed, i didn't).

Lots of wires around the horn, it is the double style with long tubes.

Where do I start on this thing?
I appreciate your help.

fuses are all ok and the new momo steering wheel has the correct contacts in place but the car did the same with the oem steering wheel.
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1976 911s targa
Old 05-01-2018, 09:47 AM
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There is normally a horn relay in the trunk fuse box. Check the relay to start by swapping for a known good relay.

I'm going from memory, but I believe when you push the horn button you are making contact to ground. When the relay detects the ground (pin 85?) it energizes the circuit to the horn.

If the known good relay doesn't work, slightly pull the relay from the socket and place a jumper wire from the ground pin on the horn relay (again, I think it's 85 but you need the wiring diagram to verify -- I know it is on my 83, I just can't say for sure yours is the same) to a chassis ground with the key on. If the horn works, that will tell you that everything is working between the relay and the horn and the problem is between the steering wheel and the relay (the relay didn't get the ground signal from the steering wheel).

If the horn doesn't work, the problem is between the relay and the horn or a bad horn. Troubleshoot by accessing the horn. Apply 12V to the positive terminal. If the horn sounds, it works. Work back to the relay. If the horn doesn’t work, horn is bad.
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You can't buy happiness, but you can buy car parts which is kind of the same thing.

Last edited by tirwin; 05-01-2018 at 01:54 PM..
Old 05-01-2018, 10:04 AM
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Tirwin gives good advice on how to trouble shoot your horn. The only thing I will add, and it's just personal preference, is that I would begin with the horn itself. Since you do get a sound of some sort, which may be the horn, you might as well do a direct connection to see if it functions fully. If it does, then follow the circuit path as suggested. If it doesn't, you know that is, at least, part of the problem.

Additionally, there is no reason why a green light should illuminate on your dash when the horn button is depressed. Can you clarify which green light it is--oil warning or parking lights? Either way, it shouldn't light so your problem may be bad grounds or miswiring. The horn is a ground circuit from the wheel to the horns so maybe there is a "leak" to the dash light.
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Old 05-01-2018, 10:42 AM
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(oops -- ossiblue beat me 2 it ) if you can easily access the horns (sounds like you can), you might want to start by confirming that the horns work and then work backward from there -- I've replaced 2 failed horns (over 60k miles) in another car, so these things can/do fail too.

Last edited by darrin; 05-01-2018 at 11:46 AM..
Old 05-01-2018, 10:43 AM
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There are plenty of other reasons why the horn might not work, my car had been fitted with an aftermarket steering column bushing/bearing that was electrically insulating the horn button/column. I found a factory part that solved the issue.
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Old 05-01-2018, 11:25 AM
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I’d try to check whether you’re getting voltage at the horn and work from there. Unfortunately, they’re kind of tucked up behind the bumper, but shouldn’t be too bad to access on an earlier car. Mine were bad, but I replaced them with the Hella Supertones. You can however try to adjust the horn to get them working as there is an adjustment screw (I seem to remember).
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Old 05-01-2018, 01:25 PM
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Quote:
Originally Posted by Jack Stands View Post
I’d try to check whether you’re getting voltage at the horn and work from there. Unfortunately, they’re kind of tucked up behind the bumper, but shouldn’t be too bad to access on an earlier car. Mine were bad, but I replaced them with the Hella Supertones. You can however try to adjust the horn to get them working as there is an adjustment screw (I seem to remember).
I don’t think that will work. 12V is not present at the positive terminal of the horn until pin 85 is grounded on the relay. You could put a meter on the + of the horn and then ground the relay but it would probably take a helper.

I just did this. Take a test light and connect it to battery negative terminal. Turn the key. Slightly pull the horn relay and touch the probe tip to pin 85. Horn will (should) honk.
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'83 911 SC 3.0 coupe (NA)

You can't buy happiness, but you can buy car parts which is kind of the same thing.

Last edited by tirwin; 05-01-2018 at 04:52 PM..
Old 05-01-2018, 02:07 PM
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Ok
I tried two relays and when I push the button they click.
Then I looked at the horn and I think I might know why is this thing not working.
I plan to buy cheap one to get me over safety.

Will ty the 85 and negative to be sure again.
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Last edited by kavadarci; 05-02-2018 at 03:23 AM..
Old 05-01-2018, 04:42 PM
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I bought the Hella Supertones too. They don’t sound super Porsche-ish but they are loud. It’s a safety device so I’ll take safety over style.
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There are those who call me... Tim
'83 911 SC 3.0 coupe (NA)

You can't buy happiness, but you can buy car parts which is kind of the same thing.
Old 05-01-2018, 04:56 PM
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If originality is not a concern try a Strobel Nautilus Compact. 130db. Small. Gets the attention of others.
Old 05-01-2018, 05:08 PM
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