18-03-2018, 08:35 AM
thanks Tony - very comprehensive. Do you see Stuart's comment about the series/parallel applying to earlier cars still then? It was the '25 wiring diagram that was confusing showing just one wire! I can see how a two wire system, if it were an earth return, can be changed at the switch from series to parallel through the lamps' dual filaments (always operating together, presumably) in an old fashioned bulb... but we change the method of functioning by wanting to select each side of the 21/6W?