Hi. Correct me if I am wrong, but assuming I have a working horn relay, if I have 12V to the post with the alligator clip attached to it, and I ground that out, it should sound the horn, yes?

 

Read this thread:
https://www.jaguarforums.com/forum/x...issues-232276/

 

Um..If you apply a ground to anything with 12volts on it, you will blow a fuse. If you are trying to energize a relay, you need to apply 12 V to one side of the coil and ground on the other side.

 

I have that same diagram in my WSM which is why I'm a bit confused here. That bullet connector, unless I'm missing something, is the last element of the horn circuit before the steering column sliders and the horn push - meaning that there's already current flowing through the relay to get there. Meaning if the relay is good, this test should cause the horn to sound.

Shorting my relay sounds the horn, grounding the circuit here does not which makes me think 'relay' but I've got four of them (three new) and the horn doesn't work with any of them. Hence my confusion/question.

Also, @carsnplanes, given that the horn button designed by Jaguar is a switched ground on that very circuit, I respectfully disagree in this case that grounding this particular lead will blow a fuse.

 

Then I misunderstood you because when you said ; "if I have 12V to the post with the alligator clip attached to it, and I ground that out, it should sound the horn, yes?", I understood you saying that when you ground the post with the alligator clip that has 12 volts on it, the horn will sound and , I'm saying that if you intend to ground that clip with 12 volts on it, you are shorting 12V to ground which will blow a fuse. If you short any wire with 12V on it directly to ground, you know you will surely blow a fuse.
If the wire you show is the ground leg for the coil of the relay and you touch ground, which would be the same thing as pressing the horn, then yes, the relay should pull and the horn should work. But that is if the wire you are holding is a ground wire and not a 12V wire which you originally said, hence my reply to you.

 

CPR999
You are correct. The wire colour (on a pre-facelift anyway) is purple and black and the horn push button send the relay trigger signal to earth. It is not a short to earth, as there current goes through the relay trigger circuit, which has a resistance.
I would rig up a test wire direct from the horn relay to the column copper wiper and see if that works. if it does, the purple and green wire is faulty. Or do a continuity test on the P/g wire.

 

Well - I figured out the solution here. I had one real issue and one I was inadvertently introducing.

The horn push on my steering wheel is just flaky - I cleaned it up a bunch and made sure the rubber surround is seated correctly around the horn button and now it's working. So I have a horn.

The relay not closing when I triggered the horn circuit - I was chasing that for a while trying to figure out how it was possible that I could read 12v through the low current side of it but not have it close. Eventually after a lot of iterative tests I just connected the relays to a spare battery I have to make sure they worked at all, and they did. So I figured something was introducing too much resistance in the circuit to get the relay to close. In the end it was actually my multimeter - if that was in the circuit (it always was so I could see what the voltage was at various points) I guess it has enough resistance in it that having it in there keeps the relay from having enough electromagnetism to close the high amperage side. I am sure this was it - the relays (low current side) connected directly to a battery close every time. If I added in the multimeter to that circuit (battery +, relay, multimeter, battery -) I could read 12v or ~4 amps but the relay won't close. This was not something I expected and a big source of my confusion.