Wiring up separate switch for horn?

I bought a TD4 at the end of January, shortly after taking delivery I found neither of the horn switches/buttons on steering wheel work. The horn itself seems fine, I left door open and used key fob to try lock car, the horn sounded. I'm guessing it's a problem with the rotary coupler and waiting for the dealer to get one to fix issue.

In the meantime it means I'm driving a car that is technically illegal as it doesn't have a working horn.

So I'm thinking of wiring up a simple push to make switch to the horn, just wondering if anyone has done this and if so did they wire directly from battery to switch to horn or did they splice into another cable somewhere, any guidance would be appreciated.

Thanks

Switch -> fuse -> relay -> horn is how I'd do it.

sijwhite said:

Switch -> fuse -> relay -> horn is how I'd do it.

Click to expand...

Thanks for that. Now to find the right wires going to rotary coupler to see if I can splice into them, altough that involves being near circuit for airbag, so perhaps not.

It's possible that a separate feed/relay is used to sound the horn than the alarm system ?......

as it had a replcement radio fitted to it

dave66 said:

I bought a TD4 at the end of January, shortly after taking delivery I found neither of the horn switches/buttons on steering wheel work. The horn itself seems fine, I left door open and used key fob to try lock car, the horn sounded. I'm guessing it's a problem with the rotary coupler and waiting for the dealer to get one to fix issue.

In the meantime it means I'm driving a car that is technically illegal as it doesn't have a working horn.

So I'm thinking of wiring up a simple push to make switch to the horn, just wondering if anyone has done this and if so did they wire directly from battery to switch to horn or did they splice into another cable somewhere, any guidance would be appreciated.

Thanks

Click to expand...

The horn buttons on the steering wheel, switch the Purple/Yellow (PY) wire (from the horn relay) to earth.

The alarm ECU does the same to activate the horn.

To put another switch into the horn circuit, you need to connect into the PY wire and use your new switch to switch it to earth.

The easiest place to access the PY wire, is in C0082 at the rotary coupler -




You could release the terminal from C0082 and insert it into a new connector with a wire running off to your new switch.

That way you can put the PY wire back into C0082, when your rotary coupler or horn buttons are sorted.

I can supply compatible connectors and terminals, or a 'plug-in' adaptor to go between C0082 and the rotary coupler.

This would have all the circuits, plus a wire of whatever length you required spliced off of the PY wire, to go to your new switch.

PM me if you're interested.

.

cremator said:

as it had a replcement radio fitted to it

Click to expand...

Yep, the radio was replaced before I got the car. Now has a a Sony CD Player. I've had a look behind the radio and there appears to be 3 wires in the original loom that are no longer connected to anything.

Paul,

Many thanks for that information, really appreciate it. I'll PM you.

Dave

PaulMc said:

The horn buttons on the steering wheel, switch the Purple/Yellow (PY) wire (from the horn relay) to earth.

The alarm ECU does the same to activate the horn.

To put another switch into the horn circuit, you need to connect into the PY wire and use your new switch to switch it to earth.

The easiest place to access the PY wire, is in C0082 at the rotary coupler -

You could release the terminal from C0082 and insert it into a new connector with a wire running off to your new switch.

That way you can put the PY wire back into C0082, when your rotary coupler or horn buttons are sorted.

I can supply compatible connectors and terminals, or a 'plug-in' adaptor to go between C0082 and the rotary coupler.

This would have all the circuits, plus a wire of whatever length you required spliced off of the PY wire, to go to your new switch.

PM me if you're interested.

.

Click to expand...

PaulMc said:

The horn buttons on the steering wheel, switch the Purple/Yellow (PY) wire (from the horn relay) to earth.

The alarm ECU does the same to activate the horn.

To put another switch into the horn circuit, you need to connect into the PY wire and use your new switch to switch it to earth.

The easiest place to access the PY wire, is in C0082 at the rotary coupler

You could release the terminal from C0082 and insert it into a new connector with a wire running off to your new switch.

Click to expand...

Paul,

Could you confirm that I'm reading things right from diagrams, my reading is that I essentially need to connect PY Pin 3 on C0082 through a switch to B Pin 4 on C0082? Or is there an easier location to connect to a good earth?

Thanks

Dave

dave66 said:

Paul,

Could you confirm that I'm reading things right from diagrams, my reading is that I essentially need to connect PY Pin 3 on C0082 through a switch to B Pin 4 on C0082? Or is there an easier location to connect to a good earth?

Thanks

Dave

Click to expand...

Dave,

Yes, that's the best way to do it

Paul.

Paul,

Many thanks for all your help. Battery disconnected, timer set for 40 minutes (to be on safe side) and then it'll wiring time, fingers crossed that I'll be beeping soon

Dave

Once again, thanks so much to Pauls for his help.

Disconnected battery had a 30 minute + cup of tea wait for airbag to discharge allowed me time to wire up switch at my desk & then about 10-15 minutes work to disassemble steering wheel cover, release terminals, connect up & reassemble. Now it's beep-beep, happy days.

Dave

Next thing will be to check out the rotary coupler, it also has me wondering that if the coupler is faulty & source of the horn buttons failure could it also mean that the airbag would not deploy if it was needed

dave66 said:

Yep, the radio was replaced before I got the car. Now has a a Sony CD Player. I've had a look behind the radio and there appears to be 3 wires in the original loom that are no longer connected to anything.

Click to expand...

Do they have plugs on them? They could be the steering wheel control leads. I had three left over after changing the head unit in my car.