DDK - Die Deutschen Klassiker

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?

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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.

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.

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

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

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

Yes

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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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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

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

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

hot66 wrote:

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

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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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?

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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.

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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 cold

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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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