Thanks for the info. Ok so I need to use a lower wattage bulb then? I did wonder. My 20w bulb was just a trial, hanging out of the control panel on the end of a wire!
I think what you say IS happening because the bulb extinguished as soon as the starter is cranked, before the engine has fired.
I shall buy a selection of bulbs and work my way up the watts until the light only extinguishes once running. Does that sound about right?
One thing I don't understand is if the voltage supply to the warning light increases once the alternator is charging, how does it extinguish?