Newbie to XJ6 series 1

Hi I’m new to the XJ6, just bought a 79 January built LHD originally shipped to Italy now British registered and largely original except for a change of colour. I drove the car last yesterday and all was well until I tried to use GPS in the cigar lighter socket. It didn’t connect well so I moved it around and something sparked but it then worked. This morning when I started the car the ignition light stays on. I assumed maybe I’d damaged the alternator in some way, shorted out diodes or some such because nothing seemed wrong, no wires off, no fuses blown etc. I had 250 miles cross country to go today so decided to buy a spare battery and drive till the first battery got flat then change it for the new one. Long story short I got back on the original battery, which is still quite happily starting the car though the charge gauge shows it as almost into the red. I think therefor it is still charging but not at the normal rate and not extinguishing the ignition light. Is this possible and if so what should I be looking at to get it back to normal operation. I don’t yet have a manual so have no circuit diagram, it’s on order but not yet arrived.
Couple more questions after the drive today:-

Should the windscreen wipers self park? they don’t presently
Should the indicators self cancel? They don’t presently.
I had problems when exceeding 80kms an hour with what felt like fuel starvation but tank, pump and filter are just new. It turned out to be the fuel filler cap which is not allowing air in so a vacuum is built up big enough to cause a problem for the pump and infact bend the side of the tank, a mighty whoosh when the cap is opened. Can the cap be dismantled and the one way valve system cleaned?

Any help appreciated.



Sorry should have read 69 January built, the 7th as it happens.




  1. Welcome to our forum. We get and receive a lot of help here.

  2. I am not sure if the cigar lighter on your car is powered battery direct or through the ignition switch. I the former, it might had stuck :closed and is draining power.

  3. I’m not sure how electricly gifted you are. If you have a VOM meter, use it. If not, get one. A cheap one will do just fine. Read battery volts with engine off. Start the engine and read again. If the alternator is working, you will see a larger number.

  4. The guage on the dash is slow and and not that accurate. It function more like an indicator rather than a true measuring device.

  5. I suspect your car has tow tanks. Do both act the same?
    and,as your car was more than likely designed to vent the tank/s to the atmosphere, the wrong cap/s are fitted. Intended for closed line to the engine Look under the right front wing. Just behind the out board lamp. If you see a canister, it is closed loop and not working correctly. If none, the vent is via the cap/s.

  6. many of the wipers need a deft nudge to park. Not intended. but it is what it is. Mine does it that way. Not the same car, but similar.

  7. I have to return my signal stalk to center. Not sure if that is intended, but many cars need that attention.

Enjoy your great find.


I’ve got a early '74 Series II and everything Carl said applies to mine. except the canceling mine cancel with an extra bonus of turning the wipers on. Only on left hand turns. When you say “red” which red? red as in barely charging or red as in almost over charging.

this I’m not so sure about on Series I but on my Series II there’s a fuse box under the dash on the left side LHD of the steering wheel, I’ve got goofy electrics, so I keep the panel cover off, and when stuff starts to act weird. like the dash lights going dim, I reach under the dash, feel for the warm fuse, and roll it in the fuse holder. Then the lights come back on.

I’ve tried to track down this issue with a VOM but I haven’t had much success. I think the wiring sees the meter and straightens up. Kinda like when the principle walked into the class with the substitute teacher; or acts like some pot smoking free love hippy and doesn’t respond. which ultimately lead me down another rabbit hole. so I role the fuses while driving down the road.

Keep in mind, I don’t buy high end Jaguars, I can’t afford them. I rescue kitties destined for the crusher. Well that’s not 100% true, my XJR-100 is like new; and my first Jaguar '88 XJS which I’ve owned nearly 20 years, Everything works If I could get it fire up. :blush:

The 3 XJ6’s, XJS-C, and XJS convertible were all headed for the crusher to be transformed into a toaster.

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The ign ‘on’ light circuit connects the ignition switch to the alternator via the lamp, Ian…

With the engine stopped, ign ‘on’, the lamp is powered from the ign key and grounded through the alternator - and lights up. With the alternator turning and producing voltage; 12V from the alternator meets 12V from the ign key - and the lamp extinguishes. A usual problem with this symptom is that the connector (black/brown wire) detaches from the alternator and touches ground - permanently lighting the lamp in 'ign ‘on’…

Check that connection first. Then as Carl urges, get a cheap, digital multimeter - working on car electrics without a multimeter is pointless. Then check battery voltage with and without the engine running - nominally, the voltmeter should read some 14V at high idle. However, if the battery is seriously depleted, or defective, voltage will be much lower - as it will with a faulty alternator. But it is higly unlikely that your manipulations with the cigar lighter interfered with the alternator…

Incidentally, if the alternator is raising the battery voltage during the test - the light should go out. It is voltage sensitive, requiring little current from the alternator. Check black /brown wire at the alternator - indeed, verify that all alternator wires are connected…:slight_smile:

Perform an external battery current leak test. Disconnect one battery clamp and measure current drain between the battery post and the disconnected clamp - all doors and consumers ‘off’. . It should read some 20 mA - if an electric clock is fitted, current may pulsate. If current is higher; there is a current drain…somewhere - the size of the leak is a possible clue to the source. 0,5 indicates a bulb lit - usually the luggage lamp not turning off. Faulty alternator diodes may give very high current readings. There is a standard procedure for pursuing current leaks - but nonetheless tedious task…

The wipers should indeed selfpark - failure is either the park switch in the motor or the stalk switch - take your pick. If intermittent wiping is fitted; select intermittent then ‘off’ in the park position. If not; select ‘off’ whenever the wipers reach park position…while considering next step…:slight_smile:

The self- cancelling indicators is a bit more tricky. There is a 'striker’on the steering shaft that releases the spring loaded stalk around the straight ahead position. The striker may be out of adjustment, or missing - try various wheel positions to se if you find a release point. It’s adjustable…

And welcome on board, Ian…!

xj6 85 Sov Europe (UK/NZ)

Thanks Carl, Mark and Frank for the speedy response, much appreciated.

I have a good VOM and have checked by connecting across the battery, which reads about 12.4 volts with the engine off and which drops to 12.2 when the engine is running regardless of the speed of the motor so fairly sure the alternator is shot. I looked at the SNG site for spares and see that on the regulator /rectifier for the early XJ6 it is clearly marked “do not earth the field terminal” and I think that maybe that happened when I was moving a connector inside the cigar lighter socket.
I have tried to prove what Frank said by disconnecting the three terminals from the alternator without the engine running which, if I read it correctly should extinguish the ignition lamp if it is grounding via the alternator but it does no go out so must be completing it’s circuit via some other path. Maybe a relay contact?
I have put an amp meter in series with the battery with everything off and there is just a draw of about 40 mA which is the clock and the memory of the radio I guess. Do any of you guys have a circuit diagram for the series 1 XJ6. or can you point me to where I might get one that I can use until my manual arrives in the mail. I have a good knowledge of electrics but don’t want to start without an idea of what things should be like. I hear at least two relays operating when I switch the ignition on but am unclear as to where they are physically or what they are doing. If someone could scan a circuit it could be emailed to me on
Thanks for the great help so far. I’ll start chasing up the self cancelling once I have the electrical issue sorted.


when I got my car I was able to solve several electrical issues by undoing the entire fuse box. I only cleaned the contact areas and thereby probably improved the ground connection of the fuse box. A lot of “Christine” style functions stopped from then on.


your electrics are quite different from the one in SII, SIII cars. Your fusebox is behind the central part of the dash and yes, I love the display of the dashboard lowered down and giving access to the electrics! You may wish to check the function of the alternator before addressing the idiot light and the voltmeter. As per Carl’s advice I made up a connector for my digital multimeter to be plugged into the cigar lighter socket. Now I have a quite precise real time view on running voltage whenever I like. BTW, I don’t think you fried the alternator - maybe there was some debris in the cigar lighter that shorted briefly, but burnt off immediately. The cigar lighter should be (?) fused and a fuse should have blown before the alternator gives. Most electrical problems on our older Jags seem to relate to lack of grounds - and this includes the instruments’ and control lights’ function.

The wipers are notorious for losing their self park ability, but the indicators do self cancel. Tank vacuum should not be a problem in a 69 Italian car. Yet, your PO may not just have “renewed” the tank setup, but replaced wit not original younger (US) parts. Maybe you get yourself the ROM and the parts book from JDHT and simply check for originality.

Good luck


Sorry Ian, saw your latest posting too late …

You’ll find a SI electrical pattern in the original ROM held available by JDHT. I’ll pm you a copy of the one in my file.

Obviously, you do have a problem with the alternator, but you might get away with a repair of the output control unit (also detailed in the ROM).

Good luck


75 XJ6L 4.2 auto (UK spec)

The S1 (non A/C) has an AC11 with external regulator & relay, any part could be faulty, these are hard to fault-find, try looking at “Coolcats” website, he has a complete diagnostic process, (as they are also fitted to E-types)

I found it easier to replace my 43A 11AC with a 65A Lucas Universal (for Jaguars & tractors)
Internally regulated, $160

also highly possible PO could have bodged wiring, cigar lighter has power from battery

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Thanx Jochen for the tip, I’ll give that a go. Keep you posted

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Thanks Jochen
I think the problem lies with the 3AW because the ignition lamp stays on even if the AL connection to the alternator is removed. Do you know where the 3AW is in the car?


usually near the alt, on the radiator closing panel
picture (green label often missing)

here is the best diagnostic guide, fellow supplies modern replacements

You sure have an alternator issue, Ian…

As Jochen says; the S1 electrics are different from later cars. With the Lucas 11AC a warning lamp control unit (the 3AW) is indeed fitted instead of a direct connection to a connector on the alternator. Still, with the brown/black disconnected from the control unit; there is no ground to the lamp, and it should not be lit. If it is; it is different circuit problem, not related to the 3AW - which just connects the lamp circuit directly to ground and breaks ground when the alternator is delivering power…

However, Jochen is perfectly right - there is no point in pursuing the idiot light at this stage. It (the 3AW) exclusively controls the warning light, and serves no function in alternator outputs - except to warn the there is none/insufficient. While the 11AC and peripherals can be tested/overhauled/replaced individually, it is a complicated test procedure, and spares may not be easily sourced - I second Tony’s suggestion; replace the 11AC with a alternator. unless you are hell bent on originality…:slight_smile:

Fitting a new alternator to existing car wiring is sometimes tricky, but Tony sure can advice on his specific upgrade - but all alternators do the same thing; charge the battery. And I agree fully with him; the chance of damaging the alternator by internal shorting in the cigar lighter is virtually nil - it just grounds or overload the cigar circuit internally, which indeed should be protected by an in-line fuse…

As an aside, tank ventilation is absolutely essential. With carbed engines; underpressure in the tanks will starve the engine, but cause little tank deformation. With very powerful EFI pumps, there will be negligible engine reaction to tank underpressure - but potentially very serious tank damage. I suggest you run the car with the tank lids ajar until the venting problem is sorted…

…which may indeed relate to a valve inside the filler lid - which can be cleaned up. When the closed tank ventilation was introduced; as Carl says a charcoal canister was introduce. Connected to the tanks, via fuel separators in the C-pillars, to a hose connected to the tank filler neck - eliminating the need for filler lid ventilation, or rather, banning them in the US. On European versions the filler neck hose was just extended down towards the ground to vent to open air - though vented lids may have been used for a time. However, the hoses, if present, may still clog - they should be checked, and if present; verified open or cleaned…

xj6 85 Siov Europe (UK/NZ)
xj6 85 Sov Europe (UK/NZ)

here is a quote from coolcats site

"3) 6RA relay

Burned or dirty contacts. This can cause low alternator output or inconsistent operation. To test, turn the ignition key to "on", but don't start the motor. disconnect the F+ lead at the alternator, and measure the voltage between this lead and ground. Should measure very close to 12 volts (assuming the battery is ok). If it measures less than 12volts, clean or replace the relay.
Bad coil. Alternator will produce no output. The dash light will glow. Test is the same as for burned contacts."

can confirm the system is hard to diagnose & repair, when my red light came on, both myself, a qualified electronics technician, and an autolec with 40yrs experience both failed to determine the cause

as I planned to fit aircon, 43amps is not enough imo, so re-located the alt from high to low mount

the big advantage of fitting the Universal Lucas is 2 wires… fat one to charge and small one to red light.
Does away with near 50yr old 4TR regulator, 3AW, and 6RA relay, and alt, mine came tested showing 75+amps

the mounting bracket is different

Hi there and welcome! Might have a dud diode in the alternator if volts are low. Also can buy the voltage regulator on line. Wipers self park but do a “dance” as they do - parking involves reversing the motor operation in earlier models - but our '72 XJ6 behaves as our '64 Mk2, so expect are same arrangement. There is some good stuff on the internet about these. Many British cars were identical. Indicators do cancel - there is a little mech on the steering column that “trips” the indicators as the steering unwinds. The fuel caps should be vented - your vents may be blocked - not difficult to check the caps. Have fun with it! We love ours, having had it for 30 years, it is still capable of impressing visiting riders. Paul

Thanks for all the help and advice, after reading the circuit diagram and the coolcat explanations I discovered late in the day that the wiring has been heavily modified by a PO in that the 3AW is there, in apparently working order, still connected but doing nothing and the 6RA relay on the right inside fender by the coil is still there but with an open circuit coil and long since disconnected. I think I’ve been chasing my tail all day and the fault is in the alternator which is not original and I guess has a built in regulator. I’m going to remove it this weekend and see what model it is etc. My car incidentally does have air-con, in fact the biggest air-con compressor I think I have ever seen, could run a small paint shop I reckon so wouldn’t have had the 11AC I don’t think. . Makes me wonder what else I’m going to find in the electrics as I progress, Good job it’s such a beautiful car with a wonderfully solid body and a sweet engine which will make whatever work is involved worthwhile.

Thanks again for all the help thus far, no doubt I’ll be picking your collective brains again before long.


You might have a Butec alternator if you have AC. The compressor should be a York two cylinder. Not sure what your proclivity is, but you might want to consider fitting components from later series 1 cars. If your alternator is above the compressor, you can swap the compressor for the later GM A6 (or modern replacement) and swap the alternator for one mounted below the compressor. That can be your choice of Lucas of the American Delco brand.

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Ooohhh, Ian, gotta love it …

Originality may not always be a purpose of its own right, but at least it helps trouble-shooting with original sources. Looks like you’ll spend some time tracking faded wires and looking up electric parts - but that’s where the fun begins: POs have seldom resorted to “funny” solutions without similarly “funny” problems …, but you know what you’re doing.

With a different alternator setup you can start into the checking routine all over again, of course.

My original PO was a Ph.D. in chemistry and - following conventional wisdom in the early 70s - considered AC detrimental to health and unnecessary in moderate climates, aka Southern England. I admit, sometimes I’m glad about his decision when looking into the engine bay of my car.

As you don’t seem to have original parts in there anyhow you might think about more modern, smaller, lighter and more energy-efficient replacement parts. Staying more original you might go for a Lucas 25 ACR that was used in SII cars and is able to power any more modern AC compressor easily and keep some amps for music and lights.

Good luck


75 XJ6L 4.2 auto (UK spec)

If original, should be a Butec, I dont think O/H parts are available

with any alt failure, check brushes

It really would be unique if you still had the 11AC alternator, Ian - but the presence of the 11AC peripherals, though disabled, indicates it was originally installed…

The change of alternator by a PO is uncontroversial - replacing a defective 11AC like for like would have been ‘silly’, whether or not AC was a PO add-on. Identifying the present set-up is of course essential, but ideally; proper testing in situ would be more prudent - requiring proper identification for proper testing, of course…

Incidentally, and just for the record; I assume you have verified alternator belt as present and correctly tightened…:slight_smile:

With a solid body, any work done is well worth the effort…

xj6 85 Sov Europe (UK/NZ)