1954 BSA B31 Plunger wiring loom

[briancairns]

Hi,
Just rewired my bike using new loom, ( using loom diagram  that i posted earlier in thread)  everything is fine except tail and break light..
converted bike to 12 v .

The issue is break light works ( engine off) fine.
However when I turn tail lights on the break light does not work.
I had a 12 led tail/brake light and it suddenly smoked and stopped working , I have put in an ordinary 12 light, this time the break light is quite dim but  when used with tail light you can't see it, but gets extremely hot. . Changed wiring around in brake switch with no joy also changed around wiring from light fitment to loom and again no joy. The bulb will only fit into bulb holder one way.
I bought a new tail light /brake fitting but no difference.
I stuck to wiring diagram which i posted earlier in this thread.

Thanks

Brian

[Derek996]

I'm not sure what you did to the LED unit that burnt it out, it shouldn't be possible as an LED will only conduct in one direction. So if you connect it with the polarity reversed it just doesn't light up.
With the bulb though you have the brake light circuit connected to the rear light filament connection and the tail light wired to the stop light connection. Swapping the wires at the light unit should fix that.

[briancairns]

Hi thanks,
I did reverse the wires but no difference. There is only one earthing point on the loom. Should I connect an earth wire from the light fitment to the bike frame?

Thanks for your help

Brian

[Spaceman]

If only as a test, it would be worth running a separate earth wire back from the rear light unit to the earth point or battery -ve terminal (I believe is a -ve earth system). I personally never rely on earth returns through the bike's tinware because a corroded bolt here or there will generate a voltage drop that will degrade the voltage reaching the lights, although less so on a 12V system. I always use separate earth return wires.

[briancairns]

Ok will try that.
Will let you know how it goes.
Thanks so much
Brian

[briancairns]

Hi Guys ,  tail/stop now working correctly with separate earth installed.

Thanks alot

Brian