Dynamo charging

[73pgsmith@gmail.com]

My 1937 Ruby has not been used for about 12 months.
Last w/e I put a drop of fresh petrol in the carb and was pleased with how easily it started.  Everything seemed to be in order - all electrical stuff working normally eg lights, indicators, ignition etc.
BUT......    The ignition  warning light would not go out - in fact it glowed brighter as engine speed increased, and the ammeter showed no positive charge [ it does show a discharge when lights switched on ]
The cut out is closing when the revs increase -  as normal, so presumably the dynamo is charging,  and  the ammeter terminals are live [from the battery ] when ignition is on and engine stationary.
Nothing has changed while it was laid up,  as far as I know.  I shall trace the wiring and check connections, but does anyone have any bright ideas as to the cause please ? 
Thanks
Peter Smith

[John Cornforth]

Hi Peter

I would suggest that the cutout contact points have acquired a surface tarnish over 12 months. Although they are physically being pulled together, they aren't conducting electricity. The dynamo output is climbing higher than normal, and the difference between the dynamo voltage and the battery voltage is driving the warning lamp "backwards".

A gentle clean of the points with very fine glass paper, followed if possible by a clean with thin card soaked in switch cleaner or meths may well restore performance.

[John Mason]

I Don’t have any bright ideas bur you could try cleaning the commutator with a little petrol on a price of rag whilst the engine is turned over with ignition switched off.

John Mason.

[David Stepney]

I would go with John Cornforth. Sounds like cutout problems to me.

[73pgsmith@gmail.com]

Gentlemen

Thankyou for your thoughts.  
I shall do as you suggest and take a closer look at the cut out and commutator.  
If that doesn't work, I shall follow Basil Fawlty's example and beat it into submission with a large branch.

Peter Smith