Which relay is my horn relay?

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neilbardsley
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Which relay is my horn relay?

Post by neilbardsley »

The horn isn't working. It works when I apply 6v directly to the horn. I have 6v on either side of fuse 3 (the horn fuse). I have a red wire coming from the horn button so I thought the right but I also thought that I have black and yellow wires going to the horns?ImageImage

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Nine One One
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Re: Which relay is my horn relay?

Post by Nine One One »

Those terminals looks as rusty as anything, your first priority would be to take the relay out, and clean all the terminals and contacts on the end of those wires? If you can get the relay box open, it would also be worth cleaning the contacts inside as well.
neilbardsley
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Re: Which relay is my horn relay?

Post by neilbardsley »

Yes I agreed but before I do what I want to try bypassing the relay. Contacting a live 6v to the out to horns. I tried that before posting but was guessing at the in and output so need more information.
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hot66
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Which relay is my horn relay?

Post by hot66 »

Neil, is that the original colour ( blue) of your 356 ?
James

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SeanP
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Re: Which relay is my horn relay?

Post by SeanP »

The wiring diagrams you uploaded have the horn wiring as black and yellow so by default its the one on the left hand side of your photo.

Get a wire from the negative side of the battery and touch it to the brown wire on the relay and see if the relay clicks and the horns sound. Looking at your picture I rather suspect that the internal contacts have corroded also
1966 912
1969 912/6 hotish rod in build
1974 914 Dead
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neilbardsley
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Re: Which relay is my horn relay?

Post by neilbardsley »

hot66 wrote:Neil, is that the original colour ( blue) of your 356 ?
Yes

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“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
neilbardsley
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Re: Which relay is my horn relay?

Post by neilbardsley »

SeanP wrote:The wiring diagrams you uploaded have the horn wiring as black and yellow so by default its the one on the left hand side of your photo.

Get a wire from the negative side of the battery and touch it to the brown wire on the relay and see if the relay clicks and the horns sound. Looking at your picture I rather suspect that the internal contacts have corroded also
Can I just earth the brown wire?

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Re: Which relay is my horn relay?

Post by Nine One One »

Nine One One wrote: Sun Jan 04, 2026 12:12 pm Those terminals looks as rusty as anything, your first priority would be to take the relay out, and clean all the terminals and contacts on the end of those wires? If you can get the relay box open, it would also be worth cleaning the contacts inside as well.
It does not matter what you touch to what, the terminals need cleaning and also the contacts inside the relay itself, if you are not going to buy a new or decent second hand one.If the contacts are crap, it will not connect or switch
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hot66
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Re: Which relay is my horn relay?

Post by hot66 »

neilbardsley wrote:
hot66 wrote:Neil, is that the original colour ( blue) of your 356 ?
Yes

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Not that it’s practical to change back, but bet it looked stunning in that blue 8)
James

1973 911 2.4S
1993 964 C2
2010 987 Spyder

1963 Honda C100 Supercub

Its not how fast you go, but how you go fast ;)
SeanP
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Re: Which relay is my horn relay?

Post by SeanP »

neilbardsley wrote: Thu Jan 15, 2026 10:34 pm
SeanP wrote:The wiring diagrams you uploaded have the horn wiring as black and yellow so by default its the one on the left hand side of your photo.

Get a wire from the negative side of the battery and touch it to the brown wire on the relay and see if the relay clicks and the horns sound. Looking at your picture I rather suspect that the internal contacts have corroded also
Can I just earth the brown wire?

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On the steering wheel horn push YES
On the relay YES
Just earthing the brown wire NO
1966 912
1969 912/6 hotish rod in build
1974 914 Dead
LI 125 Lambretta (Yeah right it’s a 125)
Mini Cooper s
neilbardsley
Nurse, I think I need some assistance
Posts: 8623
Joined: Mon Apr 16, 2012 4:31 pm

Re: Which relay is my horn relay?

Post by neilbardsley »

hot66 wrote:
neilbardsley wrote:
hot66 wrote:Neil, is that the original colour ( blue) of your 356 ?
Yes

Sent from my 22081212UG using Tapatalk
Not that it’s practical to change back, but bet it looked stunning in that blue 8)
I've thought about it a lot. Single year colour 56 Aqua Marine blue. Looks stunning. I have a photo of it on his driveway. Why the previous owner ever changed??

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“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
neilbardsley
Nurse, I think I need some assistance
Posts: 8623
Joined: Mon Apr 16, 2012 4:31 pm

Re: Which relay is my horn relay?

Post by neilbardsley »

SeanP wrote:
neilbardsley wrote: Thu Jan 15, 2026 10:34 pm
SeanP wrote:The wiring diagrams you uploaded have the horn wiring as black and yellow so by default its the one on the left hand side of your photo.

Get a wire from the negative side of the battery and touch it to the brown wire on the relay and see if the relay clicks and the horns sound. Looking at your picture I rather suspect that the internal contacts have corroded also
Can I just earth the brown wire?

Sent from my 22081212UG using Tapatalk
On the steering wheel horn push YES
On the relay YES
Just earthing the brown wire NO
Understood. Just need to motivate myself into the cold garage. I've spent the last 2 weekends DIYing acoustic panels for my listening room.ImageImage

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“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
neilbardsley
Nurse, I think I need some assistance
Posts: 8623
Joined: Mon Apr 16, 2012 4:31 pm

Re: Which relay is my horn relay?

Post by neilbardsley »

Well it's not the relay. I bench tested it. When I touched a live 6v onto the horn relay I got a faint sound. I have 6v at black and black/white. However, the brown wire doesn't seem to be connected to the horn wire. I will try again tomorrow. It's too coldImageImageImage

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“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
neilbardsley
Nurse, I think I need some assistance
Posts: 8623
Joined: Mon Apr 16, 2012 4:31 pm

Re: Which relay is my horn relay?

Post by neilbardsley »

Horn working again. I've switched to use the relay next to it. Which I think may of been added as it screws not bolts into the wall.

I've ordered some modern replacements

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“A REMINDER. I would be grateful if those members who have borrowed bits from me in emergencies (e.g starter motor, oil cooler, etc) would return them and/or contact me”. – Chris Turner RIP
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