Hello once more, last night driving home, I noticed my headlights were brighter than normal. Looking straight away at the battery guage, I saw it was high and well into the red. Then after a few miles it went back down to 13v and things were back to normal. But this wasn't to last for long. Within a few more miles it again rose to the red level and I nursed it back home at a low speed in an attempt to reduce the alternator output. Again it reduced to normal. I seem to remember there were a few issues discussed about connections to the alternator. Any advice would be very welcome, but I am preparing myself for an alternator overhaul. I also remember Jose saying that the regulator which is inside the alternator can fail.
Kind regards, Danny.

I don't see how this can be anything except a faulty voltage regulator. But, I'm only on my first cuppa coffee

Cheers
DD

Yes, the regulator is internal and could well be the source of excess volts.


However, the fascia guage is only an indicator. Use a good DVM to accurately check the voltage put puts at vaious loads and rpm's.


Carl

I bought a digital voltmeter with 2/USB charger ports and use it in my unused cigarette lighter. Just plugs in; works great!


https://www.ebay.com/itm/Dual-Ports-...a1s_joHzBko6zQ

My path was adapting my HF sourced VOM. I made a patch cord that plugged in to my unused cigar lighter outlet.


Just checked out a few AA batteries with my VOM. Each read 1.5. Marginal, but still a bit of life.


Carl

you might need to have the alternator checked, and checking it in place with the belt on it is not the way to do it. It needs to be removed and it is a pain to remove. Get the step by step instructions with the Service Manual.oo

Jose:


Why ? Is on the bench better ? Seems like in situ would be the best test.


Willing to listen !


Carl

The alternating is obviously working (producing volts and amps), thus the high voltage reading and very bright lights. It's working too well

What brings the voltage down where it needs to be? The voltage regulator.

The alternator will obviously have to come off to replace the regulator so there's no harm in having it bench tested but, really, what other fault besides the regulator is anyone expecting to find?

Every alternator bench test I've seen involves mounting the unit onto a fixture which has an electric motor and a belt to spin the alternator just as though it was mounted on the engine .....and being spun by the engine belt.

If the alternator is taken apart the innard parts can each be tested with an ohm meter and/or visually inspected for wear and replaced as needed. But over-voltage seems like a clear cut case of regulator failure to me.

Cheers
DD

Yesterday I began the "Pain to remove job" suitably called by Jose.
I am lucky to have an inspection pit in my garage.
Having disconnecting the battery I got under the car, and found that removing the adjustment arm and pivot bolts was relatively easy. The difficult part was trying to extract the alternator upwards past the air compressor and petrol return link to the compressor. I then removed the petrol link and struggled for an hour or so trying every which way to lift it out, but the devil was just not going to give in!
This called for another aproach. The route underneath was not possible because of the anti-roll bar. I then had the idea to disconnect the links to the front wishbones, I was then able to lift the anti-roll bar upwards which meant the the horizontal part actually rocked forward about 3 inches. The alternator was then easily extracted from the underside. I wonder why the service manual did not say this? I have found a local expert who says he will test the unit and replace the solid state regulator for a modest fee of £20.UKP. Happy days! Many thanks to all who have as usual been most helpful. Kindest regards, Danny.

That's the usual method, yes.

There a lots of things the service manual doesn't say . IMO some of the Jaguar service/repair literature leaves much to be desired. And the 'factory' service manuals typically sold to the public are often abridged versions of what Jaguar originally published for dealers to use


Good find !

Cheers
DD

Yahoo, Much learned. And a path to alternator wellness.


Hard to beat that!!


Carl

I would go with DOUG, and would also say its your voltage regulator.

Walter

Too many V's and "pow" !!!


Circa 1948. College chum Roy decided to recreate his high school ride.
Early nostalgia.


We went shopping in the low rent district of "used cars" On the back row, voila 29 A Coupe. Battered and worn, but ran drove quite well.
Close nough as a bas to his original 28 based car. $60 bought it/




Stage I. Cut off the top and remove the fenders. Went rabbit hunting one night. It had "modern" after market "sealed beam" head light. OK, same as his original version.


Alas, still on skinny 21" wheels and tires. Stuck in the sand. It was dark. Revved it up to try a rocking fore and back to free it. Pow ! Dark ensued. Blew the seal beams. We got it free ands went home by flash light.


The necropsy found that the source for 6 v was at the "cut off " relay on the generator. No battery to stifle the volts!!!


Oh, well, time to tear t down and bring it back. Odd, a chain at the U joint to support the torque tube. Stop clutch chatter? A's do chatter. Manageable. Just get t in or out, do not mess around.


Early beginnigs of electrickery.....


Carl

I recently dealt with, and solved this issue with my 1984 XJ6 4.2L, 88,791 mi. I was having intermittent 17.5V burst which would cause my lights to become very bright, then return to normal. After cleaning all my 37yr old ground connections and STILL having 17.5V, I purchased a brand new, name brand voltage regulator for $14 online from, www.aspwholesale.com. I wasn't physically able, at the time, to partially remove the sway bar assembly to gain access to the alternator. So, I installed the new voltage regulator onto the alternator after just removing the adjustable trunnion, using 12 inch cable ties to secure the alternator out of the way, then removing mounting bolts. I don't know, as of yet, how to refer you to my post/pictures detailing this procedure. My post name is TONYTONEM, the thread is about ODOMETER FAILURE. Start after morning coffee, finish in time for lunch. Good Luck. Oh Yeah, been driving 2 weeks, no problems, so far.