Absolutely no power to anything!

Another unexpected issue. Had what appeared to be a weak battery so bought a brand new quality one. Car (86 SIII) started just fine and I have been driving for several days. This morning, went out to prime fuel rail 3x which worked fine, door buzzer was buzzing and then when I tried to start… it harrumphed one time and nothing. I turn key to off and then to start but NOW… absolutely nothing!!

No lights on cluster, tried headlights… nothing. I put my charger/tender on the car and ran a few errands. Came back and charger light said “Charged… maintaining”. But STILL nothing. I put a DVM on the battery and it registers 12.5.

I am just baffled… assuming the battery is indeed charged, what on earth could prevent ANY juice from getting to lights, instrument cluster, etc? Almost like the bloody battery cable was disconnected.

I am charging my jump box and will try that shortly, but can I get a few tips on where to start? I know people talk about the ignirion switch going bad, but would total loss of apparent juice be a symptom ??

Thanks all… will search more on forum as I await wise council.


Bloody 'ell! Was studying the electrical chart and it looks indeed like a faulty ign switch could prevent power to cluster gauges in posn 3. So went out to check jump box status (needed to charge) and noticed when I sat in the car my USB plug LED in the lighter was glowing. So I put key in and buzzer started and turned to posn 3 and all gauges/cluster lights lit up.

I did push, pull and wiggle the ign switch unit a bit before doing this, but AFTER things lit up I push, pulled an wiggled… no sign of short of intermittent-ness. So mmmmmmmm.
I HATE this type of works sometimes, sometinmes not behavior. Gives no confidence on driving her anywhere.

I SWEAR after I removed the charger/tender pack when it said “charged” that I wen into car and inserted key and turned and there was NOTHING!

Oh well… maybe my mind is fading and the battery was actually drained. So I guess I will try to diagnose if the alternator is doing its thing properly. If anyone has a link to a FAQ or good post on step-by-step alternator evaluation, let me know.


If the alternator is alternating you should have a voltage higher than 12 volts over the battery terminals. Up around 14 at least.

I’ve also read on several forums that a bad ign. switch may do this. I’d use the car doing round trips from my home and keep a volt meter with the car, measuring the battery voltage every time I I where about to go for a drive. If the battery’s fine but not start, well, then it’s something else :slight_smile:

So more mysteries (at least to me). I started the car and she started. I was reading about basic alternator testing and put a DVM across the battery. It read 13.5 with motor running, even rev’d to 2000 RPM. Article indicated healthy is 13.5 - 14.5… so mine is low end for sure. Diagnostic article said with engine rev’ing about 2K, turn on lights, wipers and blower motor and should see 13.5-14.5… but mine lowered to about 13.1 and never stabilized back up to 13.5 or better like the article indicated.

So seems possibly the alternator is lived its better life. But man, looking at where it sits, it seems a bear to replace? This is US XJ6 with AC, so under the compressor. Is it accessible for removal from below… or do you need to take out the AC compressor and do from up top.

Finaly I turned the car off… and tried restarting… everything dead again. I attached my charged jump box and inserting the key and turning to posn 3 lit up the cluster and the buzzer. So I am pretty sure the ign switch is OK. Just seems like my charging system is
in need of work.

Thanks for the advice

Hey Randy,

On my 83 & 85 XJ6, the headlights will come on without turning the ignition on. Try to see if your works likewise. That would eliminate the ignition switch. I’m suspecting the problem is the connection at the battery. If you have a voltage load tester, it wouldn’t hurt to check the “new” battery.

Hope you are well orherwise?



sounds like a combination of two faults. Your data for the alternator certainly warrant replacement. Maybe the dying alt took the battery with it, maybe you can save the battery.

There might be a second, intermittent issue as well. I once experienced a total power out in my 1964 Ford cruising on the fast lane of a four lane motorway at night in pooring rain: all of a sudden no more ignition, no light, no instrument light, no idiot light, no wipers, no indicators or hazard lights. Thank God the car didn’t have p/s nor p/b, so I was able to merge right to the service lane. When I had rearranged my pants I gave it a try and turned the key: idiot lights on, starter turning, engine running, lights on, wipers on, radio on … as if nothing had happened. That thing never happened again, but wasn’t explained either - for the sake of safety I replaced the battery ground wire and the engine ground wire. Ignition switch would be another hot candidate for me.

Good luck


75 XJ6L 4.2 auto (UK spec)

Hi Richard

No headlights at all with key just inserted posn 0. As I said I feel ignition key unit OK.

Also found a couple videos about SIII alt replacement and seems if sway bar links removed and bushing loosened and cooler pipe feed… this allows just enough wiggle room to get alt swapped out/in

Thanks all!

About 20 years ago when I was up in Los Angeles in my 1984 XJ6 VdP, the engine died when I pulled into a parking spot at a hotel. When it died there were no warning or caution lights, no power to anything that I noticed at the time. There was plenty of fuel in the tanks. When I tried starting the car the symptoms were a combination of intermittent “engine cranks but does not start” and “engine doesn’t crank or do anything at all”. After a long expensive tow home to San Diego I did some troubleshooting and discovered that the ignition switch had failed, the internal components were melted and some of the wires at the back of the switch were also melted. I also discovered a “rats nest” of electrical wires under the driver’s side of the dash from an aftermarket security system and an aftermarket mobile phone that a prior owner had installed. I posted on Jag-Lovers a few times about this with pictures of the melted internal parts of the ignition switch and melted wires. Once I removed all of the shoddy aftermarket wiring and repaired the splices with soldered in new wire, I installed a new ignition switch and that solved the problem. I had no further problems like this. I sold that car in 2020. If you search the Jag-Lovers archives for “ignition switch failure” you will find a lot of posts about similar problems with flaky things happening with a failed ignition switch and maybe even my post from around 2000 or 2001.
The strange thing about your problem is that the power for the headlamps does not go through the ignition switch. The headlamps get their power from the terminal posts and should be powered even with an ignition switch failure. If I were you I would remove the battery from the car and inspect both terminal posts inside the engine bay for damaged, loose, or corroded wires and make sure that the ground strap for the engine is present and in good shape and tight.
Although your problem at first sounded like a classic ignition switch failure to me, it might actually be a terminal post problem instead. Especially if you have removed the battery recently and may have jostled something at the terminal post just inboard of the battery.


1 Like

Reading 12,5V the battery is indeed low, Randy - but not enough to light up lamps…

As Henrik says, with the engine running the battery voltage should be higher than while standing; the difference depends of course of how well the alt works - and state of battery. Discharged, charging voltage will be lower than with the battery fully charged - this is about a good a test for alt as they come…

However, ‘no lights’ with the key ‘on’ implies something more than a discharged battery - to be monitored?

xj6 85 Sov Europe (UK/NZ)

Thanks all. Side topic. PartsGeek has alt choices for about $100, but one Bosch for twice the price.

All are re-mans so wondering if just paying for Bosch name or worth premium over ACDelco or Remy offerings?


As mentioned earlier, check battery earth and engine earth as well, they have caused me several issues over the years and at least 1 new battery and 1 new starter motor bought unnecessarily.

Hi. This summer I completely cleaned up the engine bay… New vac, new coolant hoses, new fuel lines and inspectrd/cleaned every ground point including mac-daddy under the engine.

I will double check but feel power path is OK. But never say never!!

And on a related happy note… managed to loosen lower air shock bolt on my X358!! Woo hoo. Now will attempt to replace upper A-arm… Bigger fish to fry before I get back to my XJ6 :joy:


Re-mans are always a crap-shoot in my experience but I recently rolled the dice on a Remy remanufactured starter and it was complete and total useless garbage. Stay away from Remy. Not the same company as when it was Delco-Remy.

Ditto !

I was thinking of those terminal posts on the fire wall. Each of mine has added feeds.
I removed a primitve alarm a PO had installed. Probably saved me from some electrickery.

One of the times, I had cranking issues I found the cable end at the starter solenoid had MELTED . A new one from NAPA was more robust and all was well.

Down and under is a ground strap Right side, engine to trans connection. Subject to poor conductivity. I have a ground up in the engine bay. engine to wing wall ground point. Along with the strap from the - post of the battery Solved a session of weirdness.

A new igntion switch via David boger solved other issue.s


After this XJ8 ordeal today… 86 alt will be easy-peasy. But got it done and rewards followed!

Easy check, Randy; turn on the head lamps when the dash warning lights fail - the head lamps etc is independent of the ign key, basically relying on battery connection and ground straps…

xj6 85 Sov Europe (UK/NZ)

Trying a few things before swapping alt.

Tightened belt. Seemed a bit loose by my feel

Also tested resistance between alt body and neg terminal of battery. Writeup I read said should be 0 Ohms to indicate good ground. Mine said about 3 Ohms…that a big deal?

But need to understand… My old BMW alt body is isolated by rubber bushes so has a dedicated ground wire from alt body to block

How is XJ6 set up… can’ see at the moment. Does it have a distinct ground wire or does alt body make metal contact with bracket/block?



Sorry to be a pain but kinda thinking out loud.

So after charger completed and changed status to “maintaining”, I tried to start. Dead as a doornail, not even front lights

I went into engine bay and wiggled power post on firewall and all solid and clean. Then wiggled battery cables at battery and where they bolt on to firewall and inner fender. Again all in order.

But then for kicks I unscrewed my battery negative cutoff switch… the thing that slides in and you screw down the green knurled knob

Went inside car and she fired up immediately. WTF!!!
I cannit believe a couple wiggles and that cutoff switch is the issue

But now on to my question since I got the old lady running…

At idle the battery reads 13.7… perhaps a bit low but charging I assume

Then I turn on lights, defroster, interior lights, blower to high and pop the cig lighter in for good measure


It is my understanding that a proper charging system/alt should have dropped but then immediately raised back to charging voltage

When I turn everything back off, she does go back to charging voltage 13.7


Did not tell us about that battery switch. An invitation to the issue you got. If you just gotta have one, use a knife variety.
For me, none. Just more to mess up.

To me, the charge voltage with no load and one with are good enough.

Drat EDGE went over the edge. Everything is bonkers. From screen location on infinitum.

The alternator hasn’t got unlimited capacity, Randy - as the current drain increases, the alt ‘responds’ by dropping voltage for the duration of the load. This is just like what happens to battery voltage when load is applied - voltage drop. Perfectly normal, and unavoidable…

You have a system that seems to work as it should, and your only problem seems to be cur-off switch - and I never missed not having it…:slight_smile:

As an aside; a fully charged battery will show around 12,8V when not being charged. The voltage, with the alt running, will depend on the battery state; as above, if the battery is low, charging it acts as a load on the alt - and with a drained/defective battery, charging voltage will be low indeed. Your 13,7V id good enough…

xj6 85 Sov Europe (UK/NZ)