Hi,

My 2008 rrsport tdv8 has failed it's MOT for "horn inoperative". The horn works if powered directly from the battery and also works with the alarm if you attempt to lock the car with the door/bonnet left open.

I've checked the 2 steering wheel switches and am confident they are working correctly. Fuse 12 in the passenger glovebox fuse box in in order.

A circuit diagram shows after fuse 12 there is a relay (Relay Horn (relay 133) before traveling onto the horn and steering wheel switches.

I am unable to find the physical location of this mystery relay either in the engine compartment fuse box or fuse box in behind the glovebox.

I would be eternally grateful if anybody knows the location of this relay and is willing to share this information with me

Thanks in advance,
David

I expect its your clock spring.

That's the connection between the sterering wheel and the car, that allows the wheel to turn.

Do all the other steering wheel switches work ? and lock to lock ?

most relays aren' t replaceable the hidden
The fact that the alarm can make the horn work, i would say the relay is ok

Hi Andy,

checked all the other buttons on the steering wheel and all work as they should, I did also check the horn buttons with a multi meter and they appear to work showing resistance when you push the horn buttons.

I expected to find the relay either in the engine bay fuse box or in the passenger compartment along with all the others.

Thanks for your help

David

You won’t find the relay

I’d check on the other side of the steering wheel if you can see the horn button operating

Don’t set off the air bag !

Hi Andy,

My steering wheel is a retrimmed wheel purchased from powerfuluk approximately 9 years ago, I've stripped the two switch packs right down to their individual components and checked conductivity with a multi meter and everything checks out up to the connector that connects the wheel to the clock spring.

All the buttons and horn work lock to lock on the wheel, I'm fairly certain the problem is after the clock spring. I was looking at the circuit diagram last night and the power from the battery goes through a fusible link (17e) in the engine bay fuse box then onto fuse 12 in the passenger compartment fuse box and onto this mythical horn relay and onto the horn I'll check that out.

Otherwise I think I'm down to trying to trace individual wires through the harness. I have doubts about the existence of the horn relay myself and can find no mention of it anywhere other than the circuit diagram.

Thanks for your input it has been helpful to me.

David

The horn relay is a integral part of the CJB so you won't find it separate. If it needs to be replaced I think it may be a replacement CJB. Do you have any fault codes ? as there are some associated with the relay.

Click image to enlarge

I had forgotten to mention this (sorry) I did do a fault scan with IDD tool when I first discovered I had an issue with the horn and retrieved the following code in relation to the horn:-

B1C56-12 (6 horn relay output circuit - general electrical failure - circuit short to battery.

Sorry about the omission

David

Hi Col,

Thanks for that I've not seen that document you posted before, but I have read sometime over the past couple of days that the horn relay was integral to the CJB but was hoping otherwise.

I checked fusible link (17e) which was a dead end it's fine.

I wonder if a replacement CJB is one of the few things covered by the Land Rover extended warranty

Thanks

David

The las 2 digits of the DTC are sixty eight (I can't get rid of that smiley face emoticon not something you'll see on my face at the moment)

David

We need to check the diagram to see if the alarm activates the same relay

There is a tick box when you post at the bottom.
Click disable smiles to get rid of

Hi Andy,

It would be helpful. The alarm is shown in the diagram I have but not to any great detail. the alarm is part of the generic electronic module (D162) and connects to the signal wire from the horn relay to the 2 x steering wheel modules but placed between to two unit , so after the horn relay so I don't think that relay effects the alarm unfortunately as it would have rules out the horn relay and therefore the CJB as being the culprit.

I'm currently working my way through the individual wires to try and locate a break or a short, at least I have good weather to be crawling around under the car

Cheers

David

Ok, I'm now on the comouter and checked.

The horn and alarm both use the same relay.
So if leaving the door open, and arming the alarm sounds the horn then the relay, fuse etc is fine.

There is a pink/orange wire from the glovebox /cjb to the sterring wheel clock spring. This is then shown as a green wire in the wheel. If this is grounded, the horn should sound

I think you mean Fortunately it rules out the horn relay and therefore the CJB.
You don't want to be changing that!

Hi Andy,

I stand corrected, changing the CJB is definitely not something I would want to do or could it requires a new not used unit and requires programming with build code available only at a dealer, BIG BUCKS I'm sure.

It was the green wire in the steering wheel along with the black that I used to check the resistance when testing the function of the horn buttons in the wheel. but I never went further than the output socket of the steering wheel wiring.

There is a short cable that connects the steering wheel wiring to the clock spring I don't know if it's detachable from the clock spring or fixed in any event it's unlikely to be available to buy it may require a new clock spring after all which I believe you suggested this in your first post.

I could live with spending £40:00 to £50;00 for a new after market clock spring in my 14 year old RRS.

I'll check out the steering wheel to clock spring wiring in the morning and let you know how I get on

Thanks for all your help you have been very helpful.

David

If it is needed, you can buy the small switch to clock spring wiring harness inside the steering wheel separate. About £30.00 a new CJB would be best part of £500.00.

I am not a auto electrician but surely if you unplug the main harness from the clock spring and bridge Pin no. 3 I think, the pink and orange wire in the harness plug to a earth point if the horn sounds it is a fault the steering wheel side, could also check the continuity on the matching pin on the clock spring socket side when horn button pressed, to see if the problem is that way, if it is o.k. then the fault is the other way towards or the CJB. As Andy suggested though if you lock the car with the door open does the horn sound assuming the horn sounding with the alarm has not been disabled in the CCF files which I believe is possible, if it does sound the CJB is o.k. the fault is between the CJB and clock spring harness multi plug. That is my logic but not sure if it stands up though.



Cheers
Col

Hi Col,

I certainly don't want to have to have the CJB replaced. I'm attempting to reduce the running costs it's an expensive car to run without spending money in a vain attempt to fix the problem.

I have ordered a replacement clock spring, I'm fairly certain that's where to problem lies.

I have checked the steering wheel harness as far as the socket that plugs into the clock spring (in the photo you have attached that's the socket on the left the other two plugs go to the switch packs in the wheel and the black goes to the airbag) using a multi meter set to resistance and the horn buttons appear to function correctly, that's between the green and black wire in the socket that goes to the clock spring I thing the issue is either the clock spring or the short cable the wheel harness plugs into.

The horn does sound if you attempt to lock the car if all the doors or bonnet are not fully close I've not made any alteration to the CCF, I'm like a dog with two tails to wag that we have been able to rule out the CJB being at fault. I may go ahead and change the wheel harness along with the clock spring just to rule out it being an intermittent issue.

I think were on the right path with clock spring and associated wiring. The clock spring I ordered las night was £55:97 free next day delivery, another £30:00 for the wheel harness won't break the bank this week. I'll let you know how things go but I don't foresee any problems.

Thanks for your help with my problems it's greatly appreciated.

David

Hi,

Sorry for taking so long to get back but I've been knee deep in cables and connectors.

New clock spring arrived Saturday and I installed it straight away and it has the same issue as the old clock spring I had just taken off, still has an inoperative horn. This is where I noticed a few discrepancies between the circuit diagram and the wiring in the car, the green wire in the wheel is connected to the 2 x horn buttons when the wire comes out of the clock spring into the harness to the CJB the diagram shows it as purple and I can get no continuity between this purple wire and green, but I do get continuity between the green wire and grey with red stripe which is also connected to the clock spring the grey/red wire is twisted together with a second grey wire with a black stripe and this is the case with both clock springs.

I spent most of yesterday messing about with the CJB, I was trying to find the socket that the green horn wire connects to it's numbered as C0580-23 on the diagram. there is six sockets on the CJB (C0580 to C0585) 3 X on the front, 2 x on the rear and 1 x on the bottom. the socket I needed was either one of the rear ones or the one on the bottom, the CJB had to come out find it was on the bottom I checked out the plug for this socket looking for the purple wire that according to the diagram connects to, and could find no purple wire. I did try for continuity between the purple wire and grey/red wire from the connection at the clock spring with all the wires in the C0580 connector with nothing there.

If I have a faulty CJB as long as it only effects the horn I've decided to fit a generic/universal horn wiring harness and use the existing horn and steering wheel buttons Hopefully this will work good enough for the amount of use my horn gets. It would be a very expensive job to replace the CJB for the sake of a defective relay which can be purchased for the price of a cup of coffee, a small cup at that.

David