Thanks for all the advice on my previous ammeter queries. Thinking it through a bit more, I really think a voltmeter would be much more use than an ammeter in any case. With an ammeter I can see whether current is currently flowing toward the battery or flowing away from the battery - and as I am on 12v with LED bulbs and electronic ignition this current is about 0.8A.(It will increase if I also blow the horn and brake but I probably won't be looking at the ammeter...!). With a voltmeter I would be able to see if the battery is holding charge (12.7V approx) and if the alternator is providing charging voltage (14.4V approx). And I would see if the fuse had blown.
I can't find a 12v voltmeter that will fit in the ammeter 41mm hole - so am tempted to try an ebay LED in a blanking plate. https://www.ebay.co.uk/itm/168170228897
To avoid it flattening the battery when parked, it would ideally be connected from the ignition switch, but I am not going to dismantle the loom again at this point. I think I can swap the single bullet connector to a double on the dip switch wire (Blue), and connect between there and the nacelle earth. I intend to use the LED bulb headlight as a daylight running light in any case, so this will always be live when the bike is in use.
I used 1 of these in the ammeter hole https://www.ebay.co.uk/itm/335042996862
and made a small hole in its centre with 1 of these wired into an ignition controlled circuit(ie it only came live with the ignition on) https://www.ebay.co.uk/itm/200537741230
glows a nice green when riding along and charging and red when on and not started
has a range of colours relating to voltages/rpm
works fine for me
I use my led pilot bulb as an ignition on warning, I wired it direct to the ignition side.
and my headlight switch purely powers the headlight on/off
Quote from: Tigerfeet on 06 Mar, 2026, 08:13 It will increase if I also blow the horn and brake but I probably won't be looking at the ammeter...!)
if it's been wired as original the horn or stop light don't go through the ammeter.
This has been an ongoing debate on a number classic car forums as its a very sensible question. The conclusion is that ammeters make more sense with a dynamo where you are trying to limit loads to within the dynamo capacity and voltmeters make more sense with an alternator where you have plenty of amps but you want to know battery condition. So the general advice for cars is if you swap from a dynamo to an alternator (a common mod) then swap the ammeter for a voltmeter.
The big plus for the volt meter is that its not full current so you take two high current terminations out the loom.
On the other hand, the ammeter is an essential part of the main power circuit, so those hefty cables will still be required whether the ammeter is present or not.
The problem is that you have two nuts/studs that carry the full current and they do get corroded and or loose so they cause intermittent faults or get hot. A voltmeter is in parallel whereas the ammeter is in series.
That's true, but ammeter nuts becoming loose or corroded isn't a known problem. If corrosion inside the headlamp shell is an issue there's still lots of other screw-type connections in there for it to affect.
I've used these voltmeters, https://www.ebay.co.uk/itm/167464491323
I empty out the old broken ammeter case and fit these inside.
I like the digital voltmeter - stuffed into the body of the old ammeter. Neat! Might use that on my B25... :0)