Can anyone help me out with horn wiring? I am trying to take a feed to work a siren-change that should only be +ve when horn activated.... meter giving some odd readings off the wires coming out of the sounders behind the grill.... any ideas what is what??

 

 

I unplugged the connector in the grille and found it is + switched on the black wire, cut this and loop back to your siren controller

Well I spoke too soon, it behaves differently when it's actually plugged back in to the horn and isn't giving me the +12v for my siren change.

 

I can hear the horn relay clicking in the fusebox under the bonnet so was planning to try and tap the feed there but I am damned if I can get the fuseboard to lift out. Followed the guide in the workshop manual and it won't budge so I can't get under it to trace the positive feed output wire.

 

Anyone found another way of doing this?

Thanks; yes that is exactly the initial problem I had, the multimeter readings were not simple step voltage change to activate the changer once everything was plugged in as it should be. Solution this end was to take a feed to a low-volatge momentary latching relay to act as the change input. Complicated but sorted it.  

So did you drive the relay from the horn feed? Do you recall which wire you used?

The black; the voltage change isn't enough to trigger the change function on my siren unit, but it is enough to drive a momentarily latching relay. (Its about 2V on my multimeter)

Autodata only has the diagram for up-to 2015 vRS

Great stuff thanks

I've been searching for a relay that latches momentarily and cannot find one, will a normal 4-pin auto relay do the job?

 

If I search for 'momentarily latching relay' I can only find relays that stay latched after a momentary input. What I think I need is one that latches for only a second after a momentary input but don't know if these even exist?

Yeah, 4-pin will be fine (momentary latching meaning as opposed to a changeover relay)

Don't know if you can help me any more but I am a bit stuck with my system. I have picked up the positive pulse from the horn and it is driving a relay as you suggested. However, my siren controller diagram is no that clear and there are no written instructions to work with.

 

I 'think' the diagram below shows that the car horn would normally ground through the 2 controller wires but not sure why it can't just be one wire tapped in, makes me think it needs to sense some current flow rather than just seeing an earth? I was going to use the relay to ground the wires but not sure if this will work.

 

Do you (or anyone) know where I can pick up the negative switch from the horn ring? Is there a wire coming from the steering column that I can just cut and loop in as per this diagram?

Edited 28 July, 20178 yr by CFBScout

 

 

http://s256.photobucket.com/user/cotefarmboy/media/Capture HRT_zps3rxqb3i5.jpg.html

Edited 28 July, 20178 yr by CFBScout
Link to image

21 minutes ago, CFBScout said:

 

 

http://s256.photobucket.com/user/cotefarmboy/media/Capture HRT_zps3rxqb3i5.jpg.html

You need to stop using photobucket, with little or no warning they have made sharing images chargeable, so nobody can see the images...

Edited 28 July, 20178 yr by SWBoy

Ah ok thanks. I tried to just upload the image as an attachment but it keeps failing (only a small jpg file)

Hopefully this link works? The connections are the yellow/white wires to the right hand side.

 

https://1drv.ms/i/s!AsH8u62zUDuDg_8F1HBT_jI5kTfggw

On 15 July 2017 at 08:15, xpower said:

Autodata only has the diagram for up-to 2015 vRS

 

Anyone know what or where the module' A11' in the diagram above can be found? I think I need the brown wire coming out of this that switches the relay.

What siren controller are you using? It shouldn't be necessary to do anything other than take a positive pulse. 

 

Sorted now thanks, picked up the positive pulse to drive my relay and provide a switched earth

Every so often I will spend days scratching my head and and getting frustrated before I remember to check on here. One again this is *exactly* the problem that's confused me for a week. Will change tack and try the above 🙏

And just to close the loop on this one. Black and yellow wire from relay K14 to the two horn sounders does go +Ve on horn press but doesn't reach 12v. It will readily switch a relay though.