17-09-2017, 10:09 AM
Hi Peter
It would seem to me that you have a combination of factors. With 6 volts there isn't a lot to play with to begin with, so the cumulative effect of several small voltage drops can be significant.
I would be unhappy with any switch that dropped more than about 0.1 volts at its maximum current. For a battery isolator that means 0.1 volts at about 200 Amps when cranking, so the drop when just running headlamps should be miniscule. I don't know what type you have, the "Red Key" isolators were originally made by Hella, but there are also some look-alike ones which may not be as good inside.
For the Lucas PLC2 lighting switch, this was designed in the days when switches had to take the full lighting current, so it is of the "chunky brass" school of construction and has low resistance when working properly. It's possible to dismantle and clean these, but only for the brave !
Your LED rear lights seem to be particularly fussy about voltage, whereas a filament lamp would carry on glowing even at 5 volts, albeit not so brightly. I wonder if replacement LED designers aren't fully familiar with the vagaries of 6 volt electrics? Maybe a different brand of LED would work better,
It's also worth checking the wiring, not much to go wrong with wires themselves but where they join at each end must be clean and tight.
It would seem to me that you have a combination of factors. With 6 volts there isn't a lot to play with to begin with, so the cumulative effect of several small voltage drops can be significant.
I would be unhappy with any switch that dropped more than about 0.1 volts at its maximum current. For a battery isolator that means 0.1 volts at about 200 Amps when cranking, so the drop when just running headlamps should be miniscule. I don't know what type you have, the "Red Key" isolators were originally made by Hella, but there are also some look-alike ones which may not be as good inside.
For the Lucas PLC2 lighting switch, this was designed in the days when switches had to take the full lighting current, so it is of the "chunky brass" school of construction and has low resistance when working properly. It's possible to dismantle and clean these, but only for the brave !
Your LED rear lights seem to be particularly fussy about voltage, whereas a filament lamp would carry on glowing even at 5 volts, albeit not so brightly. I wonder if replacement LED designers aren't fully familiar with the vagaries of 6 volt electrics? Maybe a different brand of LED would work better,
It's also worth checking the wiring, not much to go wrong with wires themselves but where they join at each end must be clean and tight.