Good morning, I ve been reading archives about my issue and I have a few leads to investigate like lose connections but my problem is a bit different than what i’ve read so far.
I got a 1985 xj6 with 93 000 miles a few weeks ago and recently it has been slow to kick in on first drive of the day (could cold weather be a factor?) and by slow I mean very slow. Like 20 minutes… Battery light voltage flickers dimly on and off (never comes up bright and steady) then after a long while I guess the alternator is happy with something and produces great voltage. Then on subsequent drives it comes on right away. Morning after? Back to lazy mode again… Any ideas? Thanks!
Sticking brushes perhaps?
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Get out the VOM. Make a patch cord to connect via the cigar receptacle. Read voltage in real time under various rpm and loads.
Or, log after I had what I thought was an original idea, I learned that plug in’s exist as accessories… slick LED read outs.
Carl
Thank you all, I have put a voltmeter on the battery while exercising the rpm’s from on top and it shows in the mid 12’s. When i drive the car, both the battery light flicking lightly and dimly and the voltmeter do not show a normal condition but the alternator kicks in at some point and then i’m fine for the rest of the day.
Problem is…it takes longer and longer for the alternator to kick in, at some point i’ll have to stop taking chances…
Emissions control where i live do not check for the air pump so I think i m going to remove it all and put an second alternator at it’s place as i have read in here. Comments?
Francois,
either the production of voltage is slow - which I’d find strange - or the voltage regulator is on its way out and over-regulating.
I was in a similar situation last fall with occasional voltage spikes. A new chinese alternator set me back like 80 EUR and was installed in half an hour (SII, no AC). Then I got a NOS regulator and brushes and am waiting to overhaul the original Lucas alternator on occasion. I don’t regret having put in a crappy part so far.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec).
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Thanks. I ve read so many alternator posts on here that my head’s now spinning 
If i have to go through the trouble of removing the alternator to have it overhauled, is it better to do that and reinstall it or just go with the “put another kind in the air pump location” solution?
It’s not that hard to get the alternator out. Try changing an alternator on an Alfa transverse mounted V6! (Or a Ferarri Dino)
My other Jag is an 89 XJS conv V12 and I just replaced its alternator which was not fun so I guess i can handle an alternator on this XJ6 But talking strictly Alternator quality, is the Lucas good enough to spend money overhauling THAT one and call it a day or should i investigate as some did upgrading to another kind, maybe with more amps?
If the rebuilder is competent then it will be fine.
It’s hard to find places which rewind them here.
If the current alternator can service the loads, and you’re not planning to add significant loads, then there’s not much point in going to a higher current alternator.
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Hi Francois - I just replaced the alternator last weekend in my 85. You may have come across this tip already but it is much easier to do it by removing it from underneath. You will need to remove the 2 mounts for the sway bar to get it out of the way (and also the end links to make it really loose but not strictly necessary). But after that it’s a piece of cake compared to removing everything above it if you decide to do it from the top.
~Mike
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Stay with the original alternator position, Francois - moving it to the air pump locations is somewhat pointless…
You have of course verified that the black/brown wire between the alt and the lamp is firmly attached to the alt connection?
Three points to consider; some alternators require the lamp connection to excite the alternator to charge - loose connection may delay alt start-up.
Secondly; if the wire is disconnected - it may intermittently be grounded, causing lamp to flicker. This will normally not affecting charging - and the voltmeter should show increased voltage if the alt is charging.
The battery light reacts to voltage differences between the battery and the alternator output. With the alt charging the lamp should not be lit at all - and be fully lit with ign ‘on’ and the engine not running - does it?
Flickering means a voltage difference, which may be caused by a low or defective battery. Your symptoms may be a flat battery, discharging during the night - as the alternator, working as it should, fills it up, giving ‘normal’ indications…
Have you performed an external battery current leak test? Disconnect one battery clamp and connect a test lamp between post and clamp; if the lamp lights up (all users ‘off’ and doors closed) - you have a current leak draining the battery. Or use an ammeter to measure current - which should normally be 20 to 35 mA…
Certainly, a low battery ma affect starting in the morning - but you don’t mention that…
FRank
xj6 85 Sov Europe (UK/NZ)
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All good stuff here. Easies first. As Frank counsels. Connections and the tw wires must be sound, The jaguar mantra. Clean tighten and lube. Would not hurt to check the wires and connectors for volts flow. High resistance at a crimp???
The Lucas unit is as good as any, if in good condition. But, some say it’s capacity, just barely enough.
The rub on rebuilds is the questionable quality of some mass shops. If a well known local electric shop does this, the chances are much better.
However, should you want another brand. It is possible. Johns Cars of Fort Worth Texas offers an adapter. It allows an AC Delco unit to be installed n the same location as the Lucas. Past listers have reported success. The benefit is that an AC Delco can be found just about anywhere. I’ve done business with them and was pleased. Not the alt kit, albeit. My lump sports a giant 140 amp Delco, up high on it’s different engine.
Aye, some have mounted an AC in lieu of the infamous air pump. Why not??
Having two alternators is an interesting idea. Not that I’d support it.
My lump sports a brand new starter. Made in Malaysia. so far so good, now that I found the real issue for starter failures. Fixed.
Come to think of it. My Jeep sports a Denso starter, Asian. After over 200 miles, it failed. I got another of the same specie. so far so good…
My multi talented son is not a fan of asian electrics!! Prefers a good rebuild of an original…
Carl
The less work the better, i agree
No, i havent checked anything yet but thanks to you all i am making a list
voltmeter , battery light and voltmeter plugged in the cigarette lighter are in agreement concerning the charging status of the system.
yes when the car s NOT running the light is steady on and bright as it should. When the alternator finally kicks in the light never flickers or comes on
Battery is new and strong as i sometimes leave the car for several days without driving it and it starts the car strongly. I can start the car, drive to work about 20 minutes away with all lights on, Heat on before the alternator kicks on right before i get there, I leave the car running for a few minutes to put some juice back in the battery then on the next start it s still a quick one and alternator kicks on right away
Thanks!
[quote=“Cadjag1, post:12, topic:369842”]
“The Lucas unit is as good as any, if in good condition. But, some say it’s capacity, just barely enough”
only upgrade i might plan to make is to the stereo system but nothing too major.
“The rub on rebuilds is the questionable quality of some mass shops. If a well known local electric shop does this, the chances are much better” Fortunately i have a local shop i have used before that should be able to rebuild this Lucas.
“However, should you want another brand. It is possible. Johns Cars of Fort Worth Texas offers an adapter”
I went on his site yesterday and haven’t seen this upgrade on it. i’ll check again.
Thanks!
Francois,
what does the VOM tell exactly? What is the battery voltage in the system and what happens upon engine start?
On my cars battery voltage is around 12.6 V rising to anything between 13.8 and 14.2 V. I think 13.6 V is typically considered to be good enough.
Assuming an alt failure for the moment: the stock alt is neither underpowered nor per se bad because it’s made by Lucas. Some garden variety stereo with say 4 x 50 W max power is really nothing for the electric system, as you won’t run around blowing out the windows in a Jag anyhow. If the system ever gets to its limits it’s under severe heat when fans and AC compressor are working simultaneously.
I’m under the impression that the Jaguar people sourced the better part of Lucas products. The electric periphery of my Triumph fares much worse. The Jag still runs on the original starter and probably on the third alternator in well over 40 years. Most switches are still original as well. So, if you find a reputable shop to overhaul your original Lucas alt - give them a chance and keep your car original.
Frank has said everything about position. As long as you keep that air pump you can maintain the position as well. The good thing about overhauling is that everything should drop in just as it came out. I only resorted to the replacement solution as I needed the car for a winter journey and didn’t want to get stranded by the roadside.
So, if you’ve got the time, pull the alternator from underneath, identify the type (it might not be the original!), get the spare parts (brushes and regulator, mostly available NOS) and carry it all to the shop you trust. A couple of days later you’ll be all set and the car will run.
Absolutely no need to catch shipwright’s disease with an idea to get a bigger alt with a different setup and - while you’re at it - a more modern AC compressor and - while you’re at it - an aluminium radiator with electric fans and … 
Good luck and keep us posted
Jochen
75 XJ6L 4.2 auto (UK spec)
Depending on the year, Lucas stopped manufacturing parts, and just rebranded them. Both of my new “Lucas” alternators had Bosch part numbers stamped all over them. What tipped me off, is I had to clock one of the alternators for why it was messed up to this day I don’t know, But anyway, “made in Germany” was cast in the housing. Then I did a quick Bing (I Google has gotten too big) on a couple of the part numbers, and Bosch popped up. Then the last one I did, I saved myself $150.00 and just bought a Bosch. No green label, to me, is worth $150.00
I did a post on the steps and tools need to replace the alternator on a XJ6 Series III can’t find it anywhere.
brief overview
out the bottom is far easier than out the top.
Alternator replacement
- jack up the car and take the front two wheels off
- disconnect the sway bar completely so it’s just flopping around. a small spanner down below and several long extensions with a wobbly extension with the socket on the end to remove the nuts for the sway bar mount. The extensions should extend over the wings.
- Remove the the pseudo skid plate
- Loosen the coolant pipe brackets
- take the alternator belt off (I’m not going into the this part) because the adjust baffles me. I’m always tightening when I should be loosening; and visa versa. I must be a complete idiot.
here comes the tricky bits
6. loosen the alternator pivot bolts. This is going to require a couple really long extensions for a total of .6 meters or rougly 18" you’ll need a universal joint between the two extensions, A wobbly ended extension holding the socket is handy too. From behind the rack and between the exhaust pipe and power steering pump hoses thread the extension and I think it’s 13 or 14mm socket and extensions to the nut on the back. Oh, yea. keep a spanner on the bolt head on the other side and lodge it between the oil pan and the cross member (IFS) to keep it from just spinning and not loosening. Keep track of the spacers and the spacers’ order. it makes a difference. If you go the order wrong it won’t become apparent until you’ve got the tensioner almost tight, and it doesn’t line up.
7. Once loose, you can prop the alternator up to as far away from the engine as it will go, then extract the bolts.
8. disconnect the leads I think its either a 8mm or 10mm spanner / socket
9. Wiggling it out. This will require pushing the sway bar and heater hose out of the way. It’s fiddly but it will come out once you get it past the sway bar. If I remember correctly it comes out backwards and the mouting points are pointing to the left wing (fender).
Oh, and putting it back? As the XJ6 Service manual says do the above steps in reverse. The only thing that isn’t done in reverse is threading the alternator mounting bolts. this can be done from the front while everything is still loose. just prop the alternator up as high as it will go. This will give you access to the front and back mounting nuts and bolts.
I wish I could find the thread. it went into alot more detail cause I just did it.
Hope this helps.
Mark
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Still, Francois; do the battery current leak test - it’s a recommended precaution.
A fully charged battery should show 12,8V - at 12,4V is about half empty. However, if the alternator can keep the battery charged with the driving describe, there cannot be much wrong with it - it’s the lamp’s indications that is puzzling…
And anyone with an automatic car should have a battery charger in their garage…
As an aside; with ign ‘on’, voltage from the battery goes through the lamp and is grounded in the alternator - lamp lit. With the engine running; voltage from the battery meets voltage from the alternator. The lamp, with the same voltage on both sides, is ‘out’ - lamp light means different voltage. When ign is turned ‘off’; voltage from the alternator as the engine winds down is grounded in the ignition switch - and the lamp briefly lights up…
Frank
xj6 85 Sov Europe (UK/NZ)
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Mark:
Don’t feel bad!! I have a bench belt sander. A Hf device. Actually quite useful. Time to swap in a new belt. Old one worn out and I needed more grit to remove wood on my rustic solar lamp project. Slick system of adjusting the belt tension idler drum. But, counter intuitive. Over the years, I must relearn, which way to turn the adjusting nots.
BTW. I do admire the Jaguar link that establishes, belt tension. far more elegant than the olden slotted way USA cars used.
Carl
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- Replace with John’s Cars GMALT kit and GM alternator. More amps, and next time you can skip most of 1-9 because the alt is physically smaller. IMHO of course.
belt tensioner
It is much more elegant. I like it when I don’t have to monkey with it. especially on the power steering pump. the fine threads that collect the oil, dirt, and rubber add a bit of heat, and you have a nice gelled goo to clean off before you get started. Then there’s 1/4 turn at a time because of the tight space. It’s a bit tedious for my liking. I’m usually in a suit and tie, when I get fed up with the squeal, and decide to glove up and tighten the belt. The alternator belt is the worse. I have to change my clothes.