the issue I had with my Wolseley Hornet was the dynamo. The apparently odd behaviour of the voltage regulator was evidently nothing to do with the regulator at all, but all to do with the dynamo packing up on the job. Why the regulator kind of cut in when I revved the engine fairly hard is anyone's guess, maybe the dynamo was giving out its last gasps of voltage. Anyway I took my old dynamo to a local place established in 1962 recommended to me by an ex motor trade neighbour. They would rewind it for me, he said. The dynamo I got back after one week was not the same one, in my opinion. I suppose it might contain some elements of my old dynamo, like the main shaft and commutator, but the casing and end plates had been sprayed up and the casing was pitted where rust had been, whereas my old dynamo had a smooth casing. The fan was a different one. This was pointed out to me because the man said my old fan (which I think was cast) came off an A35, and he'd put the correct one on for me. However it was rather wavy when you turned the shaft! Anyway at £35 it was around half what I'd expected to pay for a 'new' dynamo so off I went to give it a try. It had been fitted with new brushes and bearings so I knew it had seen some work. It was a week before I got it back on the car (also having trued the fan up a bit first) and while I've only test driven the car once after fitting, all seems okay, aside from some issues I had getting the fan belt tension right as there seems to be a 'tight' spot so if the tension is correct where the belt is looser, overall you are over stressing the bearings when running. While I can't see anything wrong, again I suspect this is due to some slight out-of-trueness of the pulley on the new old dynamo, although to be honest fan belt tension is not something I checked in detail before, so it might have been like this previously. Anyway thanks for the previous advice, I've kept the pdf of the voltage regulator diagnostics for future reference, but the initial symptoms of the ignition light being on at full brightness, or fully off with no flickering at idle, were all down to the dynamo cashing in its chips. Cheers, Mick. 
I took my Wolseley Hornet for a spin tonight because it hadn't moved for a fortnight, and on getting home I noticed something odd.
The noticed events were as follows -
On driving up my driveway, I suddenly noticed the red charge light was on very bright. As in 'no charge' brightness. While still moving.
Stopping in front of the garage door on tickover, headlights on, the charge light remained bright red.
Turned off the headlights to lower the load on the dynamo, no change, still bright red.
Throttle blip, nothing. Still bright red. Revved it to about 1500rpm, the light went out. Black. Back to idle speed, the light stayed black.
Put the headlights back on, expected the red light to begin flickering with increased load, no. Still black.
Turned off the lights, turned off the engine. Ignition on again (oil lamp and charge lamp on)
Fired her up, oil lamp went out, charge lamp very bright red.
Little throttle blip, no change.
Gave it some revs again, charge lamp out, totally black. Back to idle speed, headlamps on again, charge lamp still black.
Now I know I'm not dreaming this but usually at low engine revs and/or with an electrical load on my dynamo, that red charge lamp usually glows dimly and flickers. The slightest revs normally extinguish it and then it will flicker again at idle.
I took the cover off the voltage regulator and by now under torch light, fired the engine to try to see what was happening. From the Haynes manual, what's called the 'Armature tongue and moving contact' (item 5) was up against the 'Stop arm' (item 4) while the red light was very bright, but by revving the engine directly at the carb, I saw the 'Armature tongue and moving contact' move slightly jerkily towards the 'Fixed contact blade' (item 3) and then there it stayed, even when the revs dropped back again, until I turned off the engine. That's the extent of the diagnostics I've done tonight apart from consulting the Haynes manual and trying to find a similar post on this forum.
Currently the magic involved in making a voltage regulator do its job properly is not in my knowledge base, but I am assuming something is sticking. Apparently I've got a working dynamo and a voltage regulator that cuts in and out, but it doesn't seem as progressive as it was.
Does anyone know if it is just a case of cleaning contacts with glass paper, do I spray some WD40 around, or is there perhaps a developing gremlin in my dynamo making the voltage regulator misbehave?
