Brake Light Modulators

[grandpaul]

i sometimes switch to negative ground specifically in order to use modern components. cant do it with zeners and rectifiers on the original harness

You COULD install a negative ground zener on a positive ground bike, but you'd have to isolate the heat sink, and run an eyelet connector from the zener's base to the negative terminal of the battery.

 

[Rudie]

run an eyelet connector from the zener's base to the negative terminal of the battery.

That would isolate the Zener from the heatsink, the Zener would fail fairly quickly from overheating. This happened nearly sixty years ago, when Meriden first fitted Zeners to plate heatsinks, the line workers assembled the 'ground' wire between the Zener and the plate.

You COULD install a negative ground zener on a positive ground bike, but you'd have to isolate the heat sink

Why would you bother, given the Zeners available new are unreliable and either more expensive than, or at least as expensive as, reliable reg./rec.?

 

[Rudie]

switch to negative ground

would like to know the downsides.

The primary downside of changing "ground" on an old British motorcycle is loss of information, because the wiring colour code is the primary information.

Components with diodes "grounding" through their mountings (e.g. rectifier and Zener) absent, it is possible to change "ground" simply by swapping the harness wires connections to the battery terminals.

However, Lucas specifically used plain Red wires to indicate "positive ground" and plain Black wires to indicate "negative ground". Simply swapping the harness wires connections to the battery terminals destroys this information.

Otoh, there is no technical downside or upside to either "ground". As I posted earlier, "ground" does not exist in vehicle DC electrics, DC works exactly the same irrespective of "ground", all the "negative" or "positive" prefix indicates is the battery terminal connected to the vehicle's frame or chassis.

 

[speedrattle]

i dont know of any literature on it. i have a podtronics and an ancient boyer on the one im thinking of, and i just wired it from scratch in order to fit modern fuses and connectors. the original harness was so badly messed up it was easier to throw it away than fix it.

the last time i rewired it i was planning on installing a GPS speedo and an inertial performance logger for timed speed trials. ended up not using either.

the alternator doesnt care which wires are ground.

 

[Rudie]

i have a podtronics and an ancient boyer on the one im thinking of, and i just wired it from scratch in order to fit modern fuses and connectors.

the alternator doesnt care which wires are ground.

Neither Pod nor Boyer "ground" through their mountings.

Like all reg./rec. Pod has single DC- and DC+ connections.

All e.i. are glorified on/off switches, must be connected between battery -ve and ignition coils irrespective of "ground". So, like any switch, their DC- does not change between input and switched output, they only have one DC+ connection.

Alternator generates AC.