Ignition on/off switch

[ChrisE]

Electrical ignition switch.

Please look at the photos below of two Jowett stitches. One is my 1929 and the other a friends 1927.

The right hand switch is lights and presumably the letters stand for “off”, for “S” Sidelights and for “H” Headlights.

But why are the ignition switches so different and what do the initials “C” and “1/2C” and for in 1926 and “M” and “D” stand for in 1929? Why would they be different?

The 1926 has been totally re-wired in a bonkers way with many, many too many wires, modern connectors and shiny bright cables making it far too complicated and it would be good to strip it all out and re-wire it correctly.

I wondered if "M" and "D" are "Magneto" and "Dynamo" but you'd never have both fitted so that doesnt make sense.

Thanks, Chris

[Keith Clements]

There are more people on JT more knowledgeable than me on pre-war models but my guess is that the dynamo charging rate (before the advent of regulators) was controlled by the driver, hence Charge and half charge. Later dynamos had a field coil controlled by the regulator that measured battery voltage and current being used by all the ancillaries. You would put on half charge during the day and full charge when night driving.
The M is the ignition kill position. If the car does not have a magneto then this is just a historical hangover. The terminal would short the magneto to ground prior to switching the car to OFF.
My guess is the D means drive, that is put the ignition on by connecting the magneto to the ignition circuit.
There was no need for a battery to have ignition with a magneto, but you could still have a dynamo to charge a battery for the lights.

See
viewtopic.php?t=6258
The vintage handbook shows the charging rates on page 15
viewtopic.php?p=29115#p29115
or this word processed copy by Mike Alfrey
download/file.php?id=7099&mode=view

And page 16 explains magento and battery ignition start up procedures.