Hi, horn not working on my 2004 x350, doesn't seem to be any power at horns, fusebox or steering wheel. Can someone point me in the right direction?? From what I understand the relay is built into the fusebox? Any way of testing this?? Is there something else that could cause it?? Or can someone help out with wiring diagram from fusebox?? Really at the end of my tether, everything else on the car works fine. Thanks for any help

 

Hi lotuscorty,
According to the electrical guide, you are right. The horn relay is R14 in the front electrical distribution box, which is soldered to the circuit board.

Horn circuit
There are a couple of ways of dealing with this. I had a similar issue with the relay that controls the supercharger pump. Initially, to confirm the fault, I wired in an external relay.

External relay work-around
You will have to join a wire to connector EC41 pin 5, which is the signal from the steering wheel horn button. EC41 is under the fuse box, it is black and has 10 pins. The pin numbers are marked on the plug. Use the wire from EC41 pin 5 to power the relay coil. Use the switched output from the relay to connect to F25, the horn fuse. The above diagram shows F33 and F34, but the principle is the same.

Front junction box fuses

If this fixes the problem, then at your leisure, you can remove the front junction box and disassemble it. There are two circuit boards joined by about 108 metal pins.
The best way to separate them is to use a dremel cutting wheel and chop through all of them. Separate the boards, and replace the relay. The relays are very common and only cost a dollar or so from your favourite Far-east electronics supplier. To join the boards, just put them together, and solder all the pins back together. I can give you all the details if you need more.

Regards
Pete M

 

Hi Pete,

I have similar problem with X351 (2014 XJL), is the wiring diagram same for this year and model?

Thanks
Jagpreet

 

Hi Jagpreet,
While your model is outside the range of this forum, I downloaded the electrical diagram for the 2012 X351 from here:
http://www.jagrepair.com/images/Elec...20-%20X351.pdf
Doing a word search for 'horn' eventually brings you to diagram 414-01.
There I find that the horn goes through relay R14. I would think that the front junction box is similar to the X350 one.

Relay R14 horn relay

Pete M

 

Hi Pete,
thanks for the how too.
just to check the EC41 pin 5 that needs wiring too do i need to remove the fuse box to get at the pins? (Complete novice i suspect you can tell)
thanks

 

Well test 1 is to press steering wheel horn and see you can h3ar horn relay 14 clock in engine bay fuse box
R14 is soldered in. If no click try removing steering wheel centre with torx tool and see if contacts are good. Get hold of spare engine bay fuse box or get a engineer to see if he can bypass relay.
finally if go under front left wheel surround hit horns to see if they are stuck or get a spare set of horns and test. You don't need to earth horns.
Then.check wires are not corroded or water in horns due them being wring mounted forwards.
Horn should work.