Brown wire location anybody.
 

I dunno. But, if it's solid brown, it'll be a "12 volt constant" wire. Maybe that helps narrow things down?

Cheers
DD

I’ve been through my photos to see if I can find anything and all I can see is that it seems to head towards the cruise bellows area?

You can meter it and see if it gives +12 all the time.

Is there anything in the engine compartment that doesn't work...cruise control, aux fan, and so forth? If so, maybe that is the power lead to the inoperative device.

I would guess that they made just one wiring harness for all varieties, and if an option wasn't included in that particular car then that wire was just left disconnected???

Thnaks,

John
1987 XJ-S V12

Judging by where it seems to come from (single wire from lower on motor) and the sheath on it l suspect something to do with starter/ alternator maybe.
l can eyeball my car later in the day.

Sorry Bob, some idiot cut a fibre and we've been without internet for a couple of days.

I looked in my engine bay and I can not find any wire that looks like that, although I do have the engine support in the way ATM because I have the front subframe out.

Just checked my car Brinny and l have that wire on mine. It is the feed to supplementary air valve. This is attached to right hand air cleaner backplate.
wire is routed under throttle bodies then up to connect.

The supplementary air valve on my car has 2 wires in the harness Black/Brown and Green/White. It does not,look like that.

Yes mine are the same as yours Warren I have them connected. The mystery deepens !!!

My car is UK spec, that's the only reason l can think of for difference. That wire on mine is actually brown with slate rings rather than normal lineal tracer.
l can't find very much documention (a little in the 81_88 engine info. bulletin )which includes the vacuum solonoid valve at rear of my R/H manifold which is associated with my supplementary air valve. All stock jaguar wiring.

Where is the other end going to Brinny?

Hi Brinny

A certain amount of guesswork involved which may possibly give you a clue 'or maybe not'

On my 1990 XJS V12

I've got the same single wire in a White connector exactly the same as you, except instead of it being a Brown Wire it is Yellow

'Not that I think that the Colour makes any difference' (although I could be wrong)

But on my Car, the Wire with the 'White Connector' comes off what I 'Think' is called the Supplementary Air Valve?

Where on my Car this Wire runs along the Top Closing Panel which covers the Rad and then goes into a Loom and then the Wires that come out of that Loom go into the 2 Silver Relays on the Top Closing Panel

Have a look at the Photos, as they may give you a clue

https://cimg6.ibsrv.net/gimg/www.jag...b84f698189.jpg

Single wire comes out of this 'Gizmo' and then goes into a loom

https://cimg0.ibsrv.net/gimg/www.jag...127507d767.jpg

Single Wire goes into this loom on the Top Closing Panel

https://cimg6.ibsrv.net/gimg/www.jag...295e5a68b2.jpg

Single Wire goes into Loom and Multi Wires come out, where they 'seem' to connect into one or both of those Silver Relays

No Probs Brinny

Cheers!

Brinny l suspect if your supplimentary valve is hooked up and working the brown/slate wire you have (same colour code as my valve wire) is redundant.
Jaguar tended to make changes and updates over a period of time rather than a clean cut off as they used up old wiring harnesses etc. and 1989 seems to have been a hot spot for such updates.
My own car is 1989 but l have come across many examples where wiring diagrams do not match what l actually have.
The supplimentary valve is such an example where my car matches neither earlier nor later diagrams but rather a bit of each, but it still works.
If everything related is working ok just treat the wire as redundant.