Get yourself a little multimeter. They are cheap as chips on ebay.

https://www.ebay.co.uk/itm/164779150579 ... SwKvpgWyoV

Same one as I have.

I once borrowed my bosses, had to take it back as I had absolutely no clue how to do anything with it. I asked him to explain and he said it was quite complicated. So I gave up on that

Wouldn't be a bad idea though I suppose. Even just a little test light was something I've been thinking I should have.

It is as complicated as the gearstick in our cars
You just choose what you know. Like the old village priest in my uncles town in France. He drove his 2cv only in first gear....also to the neighbouring city 30 kms away..

My other half would say that is the most complicated thing in the world

Oh dear, drove the car, it was really lovely but sat in traffic and the volts went up to 17.1 at one point and maintained high although not always as high as that. Shut the car off, back on, same. Roy at Ecas was really good and sent me a replacement VR to try.
I will report back.

Well this replacement VR works much better, it's a very solid 14.3v apart from one or two brief forays up to 15 before recovering. Seems much better anyway.

I drove it to Devon and am pootling around there now in 2cv bliss.

Further on down the line I've done about 3000 miles with this VR with my little monitor plugged in the whole time and it's much, much better than the previous one. I don't know how the previous one didn't boil my battery actually.
It does still have quite a big swing, for example if I use my indicators its like 15v briefly etc. It's always moving. But on the whole it's way better.

I suddenly thought to try the monitor in my Mercs the other day and both rock solid at 14.2v with maybe a variation to 14.3 with lights on etc. So I guess it's either not the best VR in the world, or is just the way the car works with its tiny alternator.

I know Roy gets the best he can, so I don't see any alternative anyway.