SIII Horn function

On Series III E-Type Roadster, my horn doesn’t function. How do you remove the horn button to clean contact points? If there are screws, where are they?
There is a relay behind driver’s side front wheel well. Is that a relay for the ballast resister?

Hi Mark. First post? Welcome. A couple of tips.

Conduct a good faith Search using the Search feature of the forum. You are not the first to have a horn problem and will likely find loads of tips.
Also, if you make the subject line relavant to what you need to know, as you are entering the post on the right hand side of the screen it will populate with previous posts that may be relavant. Sort of like the Search feature but in real time as you begin a post.
Try a search and then get back with us if you reach a dead end.
Hint- there are multiple reasons why the horns won’t work. Don’t get fixated on the button. If you don’t have some basic electrical experience and are not comfortable using a volt-ohm meter, we are probably not going to be able to talk you through this. It is most likely the problem is in the engine compartment, which is a much harsher environment than the horn button location.

Many thanks Harvey for your comments. The in-line fuse was blown, and the terminals on the horns were filthy. Horn button removal was easy, and you were spot-on, contacts didn’t appear to be too bad. I do understand basic electrical, I will become efficient with a volt-ohm meter!

Thanks again for your assistance, I can solve this and will return for radiator fan issues.

Morning Mark,
Welcome to the forum, I suspect that your fans may work now as the horns and fans share a fuse just over the battery.

One thing I check first on the horns is to listen under the bonnet.

Do you here the click of a relay when you push the button on the steering wheel?

On an S2 the horns have 2 fuses that can blow. One is for the relay (35a) and one for the horn itself (50a). Suspect but do not know that the S3 is similar.

Thanks L.Lynn, I didn’t realize that 50 amp fuse served the fans as well as the horns. We have added a new aluminum radiator with high speed fans, and when they come on properly the car runs cool, in any conditions.
Thanks again for your help, very much appreciated.




Hi George,

Thanks you for your comments. There is a click under the bonnet when I push the horn button. I will check for the 35 amp fuse (where is it on a S2?), and if blown will replace. As I was fiddling with the horn button, I could get it to emit
a faint sound, but no loud blast. I have run a direct line to the horns, they both work. Many thanks for your help, very much appreciated.



If that click is the relay then the 35a fuse is fine and the problem is not at the steering wheel.

On an S2 the 50a fuse is for the horn itself (#3) but S3 may be totally different.

If the relay is working and the horns aren’t (yet work with a direct line) then I would be looking at connections along the way - starting at the horn & relay.

On an S2 the relay is behind the battery (there may also be an alternator relay and AC relay back there too) but listening for the click should tell you which one. If unsure, you can usually put a finger on a relay and actually feel it click.

I’d start by just wigging the connections (relay first, then horns) and if no joy, get the multimeter on them and confirm continuity & voltage.

Thank you again for your comments, they are so helpful. The fuse chart is different on a Series III than an S2, there is no 35 amp horn fuse. I checked the diagram. I’ll respond more after I work a bit further. Thanks again,



Though, given that your horn makes a slight noise when you press the button, it clearly isn’t a fuse issue, I am mentioning this as it might be an issue for you or someone else in the future. The Series 3 wiring diagram that I have shows that the green wire that goes to W1 of the horn relay IS fused via the 35A Fuse #7. Maybe my diagram is incorrect, or doesn’t apply to all S3 model years, but I mention it just in case… Good luck tracking down your problems.


Pardon my ignorance, but I assumed that the S3 cars were like the S2 cars, where the horn is on the stalk, rather than the center button…

Many thanks for your comments. I will search for that 35 amp fuse for the green wire. We have a 23 year veteran Jaguar parts man in our warehouse, and he swears that on any given day there could be any color
wire used for any application. Sure can be frustrating when attempting to follow a schematic. Thanks again for your great help.


Hi Robert,

Thanks for your reply. Both are true, the S3 cars have their horn button on the center of the steering wheel, while the S2 horn buttons are on the end of a stalk.

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It makes for a good story, but I’d like to see real evidence that any car left the factory with any other color than green wire for a fused, switched-by-ignition power feed…

It could be like a couple of the International Scouts that I’ve helped friends with, all the wires are green. They were labeled from the factory but those labels are long gone on 30-50 yo cars.

It sounds like you have ruled out the low current path from the horn button to the relay. If the horns work when wired directly and only croak when using the cars wiring, I would say that in general some massive corrosion and therefore resistance has built up in the path from the battery to the horns. The trick is finding it and dealing with it. An ohm-meter will of course probably show close to battery voltage at the end of the line but when you try and push some serious current/amps through the wires, that is where things may be breaking down. Changing the relay would be a cheap rule out. After that, all the various bullet and spade connectors are suspect. Finally, the wires themselves will corrode on the inside. If, as your original thread title suggested, you are doing a concours restoration, I would just plan on all new everything (harness and relays) which will most likely fix the problem. Nice reproduction harnesses are not cheap but will solve a miriad of problems.

Delete. Missed where OP checked function with direct power.

Hi Harvey,

Thanks for your continued flow of information, very much appreciated. As I work thru the problems I find additional issues that need to be addressed, holding up progress on the horn issue. Your wiring article
on Road Island Wiring was quite interesting. I didn’t realize they offered Jaguar harnesses, I thought their specialty was American Antique vehicles.

I’m actually trying to solve two problems at the same time: fixing the horn and the cooling fan operation. This poor car has overheated so many times I am getting concerned that damage has been done to the
inner workings of the V-12. We replaced the stock radiator with a new aluminum unit and the accompanying high speed fans. This set up will maintain a cool operation of the power plant when it works properly. Last Concours I entered the car, completed detailing
and drove onto the show field. The car looked fantastic but unfortunately is belching coolant all across the field to our location. We have several knowledgeable members in our club, and the consensus was that the radiator cap wasn’t fully seating in the mouth
of the radiator. A quick trip to the hardware store for a plumbing ring washer cured the problem until I could get home. No pressure was building up in the system. Quick measurements revealed the cap doesn’t extend to the bottom of the entry neck of the radiator.

Back to the wiring, as I progress thru I’m cleaning every terminal, replacing relays, and the thermostatic otter switch. I am also working on an automatic Series III roadster, and am now convinced I should
replace the engine harness as opposed to all of the work of restoring the existing unit as I have the intake manifolds off and the master cylinder removed for easy access. I’m going to cause a national shortage of shop towels in the near future from the quantity
I’m going thru!

Thanks for everything Harvey, all very much appreciated. I have renewed confidence.

Mark Short

Thanks for your email. That was one of the first things checked, then we proceeded to the horn button, then to the relay. We are now on a current chase, cleaning all wiring, terminals, and connections and
checking continuity.

Thanks again for your comment,


Hi Mark,
I’ve read through your replies and I’m not clear that you found and checked the inline fuse that I mentioned earlier? It ‘lives’ on the frame rail just above and behind the battery. I had mine burn out and it took out the horns and the fans, if you’ve installed uprated fans this seems like a strong possibility. Sorry if I missed that you’ve checked this fuse.