.After some deliberation I have today had a Dynamator (alternator in a dynamo casing) fitted and also the car converted to negative earth. I chose what I thought would be a suitable 'old time' garage i.e. familiar with classics......not so sure I made the right choice (of garage) now! Please read on.....
When I picked the car up I was assured it was all done - albeit, the Dynamator installation instructions were apparently useless - but that the voltmeter didn't work as it was broken
. I did query that as it was virtually a brand new Smiths meter and it was working perfectly well when I took it in. The garage said they even had it independently tested by an electrician who was working next door and he confirmed it was kaput. Could happen, I suppose! He also told me that the LED lights that illuminate the voltmeter and the ammeter didn't work but, again...…. they did before! The back lights still work on the oil pressure and water temp gauges....and they are all wired through the same electrical connector into the lighting circuit.I was also told that a couple of blown fuses had been replaced. I thought there were only 2 fuses anyway and if they had blown then I wouldn't have been able to get the car to the garage in the first place.
On the 4 mile journey home in ''rush hour' traffic I noticed the needle on the voltmeter did move over to the right but to just about '11'. Previously, with the dynamo, it usually went to '13/14' before settling down at between 12 & 13. The battery is just a few months old. Surely the voltmeter can't be just a bit broken? It either works or it doesn't.
I was also concerned to see the temperature gauge moving over to nearly 180 when there was no sign of overheating. This was the problem I had experienced previously. then I fitted an electronic voltage stabiliser. Literally, just had a thought now.....are these gizmos polarity sensitive? By changing from + to - earth has it broken it? Do I need a - earth stabiliser?
I've already spoken to the garage to tell 'em about the temp gauge and they've offered to have a look at the car next Thursday. I've not mentioned the 'half-working' voltmeter yet. Before I do so - just in case he tries to fob me off or blind me with science - I'd appreciate some advice please about why the voltmeter doesn't appear to be working properly. Why would it work perfectly well with a dynamo and then not with an alternator. If it affects anything, the Dynamator does seem to be working i.e. when I blip the throttle the ammeter needle whizzes over to +15 or so before immediately settling down to just into + territory.
Any ideas why the back lights on the voltmeter and ammeter would stop working?
As ever, many thanks in advance for any advice/information. Forewarned is forearmed and all that!
Some people around here give advice about the colours of the wiring as though that's the answer to everything, and sometimes it is, but after 50-70 years you don't know what's been done, especially if someone is exploring their new purchase. 
