Hey forum, long story short, 2 weeks ago all of a sudden jag didnt want to crank, also turning the key in any position didnt do anything, no dash lights, no radio, no crank, however interior lights and clock was on. After walking around, hitting tyres, relays, battery terminals, key switch it did start and then everything was back to normal.
Today i was testing smth at idle and car just died, again same story, no crank, no lights, key doesnt do anything.
I got to ignition switch that looks like this


not sure if this is correct troubleshooting method, but i did test voltage at fat brown wire, its 12.5 with ignition in resting position (all the rest is 0). Then when i switch to 1st accessory, fat brown reading 0 and other wires still reading 0, so as on any other positions including crank.

from what i know fat brown should always have 12v and then each connection should show 12v when you turn the key, right?

Also i not sure if i can service this particular ignition switch any further without breaking it.

Thank you

Update: ok, after an hour or two of basically doing nothing meaningful, it did fix itself and now works normally i took the chance and tested voltage at every wire when thing works as it should and yes,
brown 12v always
the rest of the wires getting 12v according to the key position, so indeed my problem was that a) brown wire was loosing voltage as soon as key is turned and b) rest of wires didnt have any voltage, probably since brown doesnt have any.

So at the end of the day i guess i should buy another NLA thing

 

Why do I think this really is your transmission gear selector position switch that’s acting up? They can be so finicky. You think the car is in park and the switch thinks the car is not in park!

these things do tend to fix themselves and then break themselves very soon after. A good wiggle in park while cranking helps…. You also seem handy with the wiring diagram and a test tool so go find out if it’s the neutral safety switch.

 

If you've got no dash lights, it won't be the transmission rotary switch. It's far more likely to be the ignition switch as you've mentioned or else the bulkhead positive or negative terminals. Start by disconnecting, cleaning and testing the continuity of both the positive and negative bulkhead terminals.

Good luck

Paul

 

i dont think its a terminals, my car is pretty clean, all wiring in a very good condition also battery is basically new. There is literally nothing to clean, its as clean as it can be.
Another few things that might give some clues

when i tested the fat brown wire on a dead car, my test light was blinking, but multimeter was showing 12v stable volts, i didnt pay much attention(thought my test light is acting funny) But then a retested it when everything was normal, my test light was showing stable 12+ volts on fat brown, as well as multimeter.
my multimeter is really cheap one.

Does it ring a bell?

 

I had a difficult time finding the specific '92 switch. But what I later discovered is that the only difference is the wiring connector. I can't tell you which specific year ignition switch will have similar wires (but a different connector) but if you're willing to swap some connectors around then I'm pretty sure several other years will fit.

 

Please share!
I also noticed that i.e xj12, xj6 1992+ ingition switches look identical except for the connector, which i dont really care i can always solder wires directly on the switch

here is an example of switch that looks like mine
https://www.ebay.com/itm/22524093601...Bk9SR4KH44WfYw

 

Mine had an older, round style connector. If you can find one with your same connector then snap it up.

If you can't find one with the same connector then simply note the number of wires on the replacement and then make your own connections. I'm *pretty* sure most of them have a similar number of wires

 

Greetings from HK.
My 1992 XJS has experienced a similar gremlin ever since I have owned it. I can drive daily for months and never experience the issue, then, it happens five times within the course of a week.
When I turn the key over, warning lights on the dash light up but no ignition, no sound, nothing. The first time it happened, I thought it was the starter; then something to do with the ignition switch. Its impossible to get my garage to diagnose it because it never happens when I take the car for its MOT.

Then, I read that it could be related to the gear shift. So, when I turn the key and nothing happens, I return the key to off and move the gear shift from park to drive and couple of times and back in park. Wiggle it in park.This always works.

From owners who have had this problem and "properly fixed it," what part(s) should I replace?

Many thanks,
Charles

PS I will issue another post about my XJS and Daimler Double Six Insignia soonish.
But, thanks to the advice I received on this forum and the brilliant stickies from my fellow Australian, as soon as I got my XJS I replaced the cooling hoses, water pump, alternator (with a WOSP), thermostats, water rails and grommets, expansion tank, tie rods, ball joints (Lemforder) gearbox filter, ignition coils, plugs, rear wheel bearings, etc., I have had three great years of trouble free driving except for a cracked windscreen! Once I bled the coolant system as recommend on this forum (thanks Greg), my temperature gauge has never crossed the center line. The XJS has been a dream and I find it hard to jump in the Daimler, which has generally been as tough as nails since I purchased it. Nothing runs like these V12s if run regularly and maintained.

My next "project" will be to replace the cross-over pipe with a stainless steel pipe and add two SPAL fans; perhaps with a aluminium radiator. But I am not yet convinced a new radiator is really necessary.

 

If your cooling system is fine, Charles, leave it alone! And congratulations. Jaguar's only failure with the XJS was in not getting it across how good the car is!

 

Not sure if this relates to the later switch it appears is being discussed.

But

Who know, the innards are probably the same.