Author Topic: Can anyone tell me what the letter C and L stand for on this light switch ?  (Read 1523 times)

Offline Stephen Arsenal

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Charge ? control ?
L Live/Line
Hi guys,was told this is an old BSA switch,it fits perfect into the divers headlight mounting.I´m trying to fix the wires into the back,but is proving very difficult .
There are markings on the rear,L,+D,H,T,SH  (not sure what +D stands for)?
Any suggestions would be welcome
Any directions of which coloured cable goes into which clamp,would be even more helpfull.Not sure if there needs to be a bridge between two of the clamps-cheers-steve
ho ho ho

Offline iansoady

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At a guess, Charge, Light (side & tail), Headlight.

Those switches can drive you mad. For the one fitted to my Velo which was similar (but slightly different) I found the best solution was to draw up truth tables for each switch position and note what connected to what with an ohmmeter for each position. Took time but eventually gave me the correct connections.
Ian.
1962 Golden Flash (arrived)
1955 Velo Viper/Venom (departed)
2004 Triumph Tiger 955i (staying)

Online bsa-bill

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Oh yes - been there
Could not work out how it could possible work, my old Flash switch is similar but has an internal connection which explains how it works once you discover this fact.
the one I was using had no such connection but was supposed to have an external one (little arm connects one terminal with the centre pin ) but this was missing so much head scratching went on until I eventually bought a new switch and all became clear
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Stephen Arsenal

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Thanks,why would there be a charge switch ? what has that to do with the bulbs ?
ho ho ho

Online chaterlea25

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HI Stephen,
The charge position switch is pre 1936/7 when the CVC regulator appeared
Before that the "C" position fed the field coil through a resistor (sometimes mounteo on the back of the switch)
When the lights were turned on the field coil was connected directly,
The supply for the field coil came from an adjustable third brush in the dynamo

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Online groily

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    • www.brightsparkmagnetos.com
Could it be because it was originally for a bike with an unregulated 3 brush dynamo Stephen?
In which case, you'd expect to link D, via the switch, to a feed for the field coil(s) to support loads or cope with a flat battery? Lots of varieties (with various levels of subtlety) of the genre, but all primitive compared to the sophistication of a '50's BSA!
See, just for example, what Austin Seven cars used in the pre-war era: www.da7c.co.uk/technical_torque.../threebrush_dynamo.htm
Might explain the D connection on the back? C on the front face could be Charge, or maybe 'Control Brush'.
No matter - Ian's 'truth tables' will have it doing the things you need, if you want it to, whatever it really is!
(Just seen John's post . . . there we go)
Bill

Offline Stephen Arsenal

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Thanks for your quick replies,so in a nutshell,I ignore the +D clamp un the rear,and the C position switch on the front,and make a truth table ?.My fame is a positive,but the switch is isolated anyway,so should´nt be an issue ?As I have only 4 wires,in theory I should only really find the main cable power source(which I think goes from the battery,to the tailight,and back up the fame to the switch)??.Anyway,thanks again..this switch is the bees knees,it has a deep throated click,each time its switched ,and is quizte heavy too,nice piece of work .
ho ho ho

Offline Stephen Arsenal

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Thanks guys,everything sorted,took a while ,contact roller was´nt connecting sometimes because of ingrained hardened old grease on the blind side the screw clamps.
ho ho ho

Offline wilko

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