Ignition Switch Troubles

Hi all, I am running into some electrical issues with my 1992 XJS. When I have my key in the “off” position and ready to pull my key out, my radio glows as if it has power. My radio has not recently worked with my key set to run or accessory. In addition, I have some dim glowing idiot lights on my dash that I cannot diagnose the cause of them being on. The car also likes to drain the battery if I leave the battery connected beyond the time that it takes me to run the car. My steering wheel also does not seem to lock with the key off. Could this be an ignition switch out of index or possibly a bad lock cylinder? This issue has been pestering me for a while now and I am not too familiar with these Jaguar ignition systems. How hard is it to replace the switch? What is involved in pulling the switch? Thanks!

Sounds very probable.
Before you decide to take the switch out though get a multimeter, remove the plug and check the connections according to the electrical diagram.
Also check if it makes a difference in your battery drain when the ignition switch plug is disconnected.


Any chance you have 3.6 or 4.0 version…?

Any chance this could be blown diodes in the alternator? I know they cause some weird symptoms sometimes.

I have a bit more information after I pulled the switch pigtail. With the switch in position #1 (accessory) I have nearly 4 ohms from my hot lead(B) to my accessory feed (WK). The resistance in key position #2 and #3 seem to be ok. With the switch hooked up, my WK wire is cold with key out. Yet the radio wants to run. Alternator does charge, but I have yet to dive into the diode idea. Thanks again and all help is appreciated. My local NAPA dealer said that this switch, if needed is hard to get locally.

Generic ignition switches are not hard to find. Pretty much any of them will have off-acc-run-start functions and hence can be connected up to work. You’d just have to mount the switch somehow, and get used to using a different key. Of course, the steering would no longer lock.

Waaaay back in the day my parents’ 1969 Volvo was proving anything but reliable. On cool mornings it would refuse to start. One day I pulled all the spark plugs and gapped them down to .025" and it started right up and ran great. That worked until the folks took it in for a tune-up and apparently the mechs either replaced the plugs or gapped them back out to .032", and the next cool morning it wouldn’t start again. We went back and forth on those plug gaps for a coupla years, with me unable to convince my folks to quit taking it back to the dealer so they could screw up the plug gaps again.

Well, the problem clearly was weak spark, evidently due to a bad ignition coil. That should be easy to remedy. When I got in there, though, I discovered that on a Volvo of that era, the ignition coil and the ignition switch were all one piece, connected with an armored conduit in between. And the coil end of that assembly bolted into a huge opening in the firewall. Unwilling to pay Volvo prices for a replacement assembly (complete with rekeying), I just bought a generic high-performance coil and a generic ignition switch. Filled in the gaping hole in the firewall with a piece of aluminum. Handed the folks a new ignition key, they got to continue using the original key in the door. Car ran great from then on regardless of plug gaps.

The new ignition key did look like something that would fit a padlock rather than an ignition.

Thanks for your reply. I enjoyed it as I have enjoyed your book. Never worked anything fancy like aerospace, but as a humble retired marine engineer I am very familiar with adapting. Believe it or not, when your ship is in the middle of nowhere, it is very hard to get parts for your pneumatic boiler controls at your local hardware store. The radio running with the key out is a real head puzzler, but that’s probably why I have the car… it keeps me clean and sober. On a lesser car or my son’s go kart, I would set up toggle switches below the dash. Take care!

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The radio should have an always live feed for the station memory. You could have a fault somewhere in the radio itself or the wiring to it that is allowing that 12V to go places it shouldn’t?

My car is an XJwuzza six. I suspect the ignition switch is the same or similar.

Mine started with odd symptoms. they got worse and more wide spread. i did not realize the switch was the culprit for a spell.

I removed it. Not hard, just fussy.

Ruined it!!! Opened it and small bits flew… then I read elswhere that one should open the switch in a clear plastic bag!!!

Lots of corrosion and hardened goop inside.
Very loose as well.

A NOS unit via David Boger of everydayxj and so many things now fixed!!! Good guy and we see his posts here from time to time…

Side bar: I built a T Speedster from junk circa 58. I used a series of WWII surplus toggle switches. A certain up/down combination and the ignition was charged. One in the row cranked the engine. Looked slick, worked slick!!!

Just recently someone posted a great description, including schematic, of a push button replacement for the electrical part of the ignition switch. You would still need to decide what to do about the steering lock, and what to say to your insurance company about not being able to lock the ignition.

Thanks all for your responses. I went through it today with my son. We found that the radio run feed was hot at the fuse only with the ignition off, which was incorrect. I removed the radio run fuse, and tapped into the cellular phone feed, and it worked! It was very interesting! Apparently, part of my fuse block failed. Thanks for all of your comments and help!

I’d be worried about that. Those things don’t commonly short. They more commonly develop bad connections that result in heat, sometimes melting the structure. If a melted structure shorted out your fuse block, I’d wanna know about it.

Good tip! I will be sure to check the back side soon. My battery is disconnected now anyway.