Thank you. The alternator for a 94 XJ6 is available and I ordered one which should be on its way. It also appears to be a 120 amp unit

 

Rock auto sell alternators relatively cheap, bosch and deliver quite quickly.....just had a local mechanic put one in to my six and along with a new battery all seems good again.....phew

 

This is probably coming too late, but changing the alternator on the V12 is not that difficult if you work from underneath, just did the job this summer. When you loosen the anti-roll-bar on the right-hand side you can easily slide it out from below without removing the belts or radiator. You may need a variety of sockets, ratchets and extensions, but once you figure out how to do which nut, it's fairly easy.

Regarding the voltage issue, it is essential to check the wiring and grounds, especially if the car was flooded. According to my research, the batterie+ cable in the trunk is connected to the jump start port in the engine bay, so measure voltage and resistance between these two in order to see if there is a bad connection between alternator and battery. Also check the idle speed, below 800RPM the alternator will very likely not deliver fully. If that doesn't reveal any issues, check the alternator itself, has it the correct spec (if amperage, voltage or ports are different, it is very likely that it doesn't fit/will not work properly). If it has been poorly (re)built, it might also be causing issues, so you might have to look for another one.

 

I did sell the car as I wanted to close the book on the XJ40 and move on to something older. Probably it was a wiring issue, but working on the XJ81 engine was just hell. No mechanic in my area would touch the car, so I sold it to an enthusiast who exported it to Croatia,

 

I'm sorry to hear that. So you sold both of your XJ81? From my experience selling a XJ81 basically means giving it away because nobody will be willing to pay a reasonable price. That's why I still got mine. I've put so much time, effort and money into it, I will not give it away for a few bucks. Any other old car I would buy as replacement will eat money anyway.

I know the issues with finding a good workshop, I've moved on to doing everything myself. Unless the job requires special tools or 4 (or more) hands. Luckily there is a garage nearby that is not afraid of a Jaguar V12, they did a couple of jobs on it (like renewing the lower front bushes which basically required to drop the whole front subframe), but you have to tell them precisely what to do and what not. Don't go there (or anywhere else) and say: 'There is something broken, please fix it'. They will either fix nothing at all or tell you 'We fixed something, we believe it was broken'.