Hi all,

I have 90 xjs convertible. I've been working my way through the major issues and am starting to tap at the minor ones. That being the case, I have a number of electrical things not working (or mostly not working). For example, no horn. So last week I checked fuses and relays. In the drive way, still no horn. However, a few minutes later on the road I got horn. Later again, no horn.

I checked fuses on a few other creature comforts (clock memory, cigarette lighter, etc) and while all seems fine, these don't seem to be working. Any ideas as to where to go with this issue is much appreciated.

Tony in NM

 

When you checked the relay, how did you do so?

It's a very simple circuit that is easy to test if you have a voltmeter. First remove the relay and check that you have 12v on pin 30 of the relay base (brown wire). If you do, then using a bit of wire jump pins 30 and 87 (pink/yellow wire) and the horns should work. If they don't, then you probably have a wiring connection issue between the relay and the horns (there are two horns).

If the horns do work, then check that you have 12v on pin 86 of the relay base (green wire) with the ignition in position 1 or 2. If not then then check the other fuse (cooling fan I believe).

 

To clarify, did you check *both* horn fuses? And when you say you 'checked' the relays....what exactly do you mean?

Very often intermittant electrical problems are caused by poor grounds and/or dirty/loose/corroded connections at the relays, switches, wiring junctions etc. In the case of your horns I'd begin by making sure each horn has a good ground and the wire connectors and terminals are clean and tight.

If you have a test light or meter you can do some more in-depth testing, if needed.


Here is a good wiring diagram for your car, if you don't already have it. The horn is covered in Section 18.1

http://www.captainjaguarscathouse.co...ec%20Guide.pdf

Cheers
DD

 

Hi there,

By check the relay, I mean I pulled it out and replaced it with another. I also made sure that the contact was clean. I also did the same for the fuses (though I can't remember if I checked two fuses or one). As I said before, it didn't work. Later when I started the car the horn did work a bit later on the street it didn't work so I wondered if the engine heat may have had an effect on some connection.

I will check the ground as someone mentioned.

Thanks for your help so far.

Tony

 

Unfortunately, just swapping a relay does not tell you much other than the relay might be faulty. To solve your issue, you will need to do the testing/inspecting outlined above.

Although possible, engine heat is unlikely to be the root cause unless a hot engine has physically abraded some of the wiring.

 

So you have an intermittent short or open. Tie something around the horn to hold it down and run though the circuit with a DMM until you find power, you problem is where you lose power obviously.

Also do a quick check for continuity at the horn switch ground and the ground for the horns themselves. ( do this first obviously)


here is the diagram

 

Because the horn is intermittent you have a bad connection somewhere. I would start under the steering column, there is a wiper that contacts a brass collar this gives the connection up the column to the horn button. If you use a bit of wire and short the wiper to ground the horn should sound. If the horn is still intermittent then work along the circuit (the next thing is the relay), pull the relay and check for continuity between the wiper and pin 85 of the relay wriggling the wiring as you go.