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[Barry N]

Don't think I'm that lucky! I have just hooked the loose bulbholder up to a spare car battery and it lit up ok (as it does on the bike) and when I touched it to a steel cabinet it continued to light and without sparking - unlike when it is fitted to the bike (when it sparks the headlight against the nacelle and kills all the front lights, including the speedo/ameter lights and the tail light). As I said, the indicators and brake light are unaffected. Clearly something else is not right and I am now at a loss as where to look next!

[WannaBRetired]

So it works OK until you fit it into the headlight, then it shorts? Please don't take this as patronising, but is it wired up the right way round? The only other thing I suppose is to try insulating it from the shell (I wouldn't trust it, though) or replace with an Ebay cheapie to see if that works. (The ones on Ebay have a rubber grommet that is slightly small but work fine with a bit of tape around the grommet.)

Otherwise, cue electrical experts please, which I'm not!

[Gwilly]

Well done Barry and Wannaby, sounds like you've tracked the culprit through a process of elimination.

If there is only one wire feeding the holder then it should earth back through the reflector and rim,but only after the current has passed through bulb... Same as the two side lights on the nacelle.

It seems wannaby is right and there is an internal fault with the bulb holder,its giving power to the bulb but also shorting straight to the metal holder, which robs the other lights untill you disconnect the holder from the reflector... Not sure what the steel cabinet has to do with the price of eggs.

Just replace the holder and all will be sorted..... cheers gwilly

[Frank]

Sounds like a fault I had. Turned out to be a faulty headlight bulb, even though it lit ok. Could be that or a faulty pilot bulb. High resistance to earth. Dont be fooled by the fact it lights ok.

[Barry N]

This is so weird!

As I was still having no luck tracing the fault, I tried swapping the spade terminals around on the pilot light just to see what happenned - and BINGO - problem solved! Or is it??? Because during my checks I carefully marked the two spades to ensure they went back the same (same way that they had been for four trouble-free years in fact!). It's as if the polarity has somehow been reversed for some reason (and no, the battery has never been fitted the wrong way!). So for now, it may (or may not!) have been fixed. How could this possibly be?

[Norm]

Barry, I would think pretty straight forward, bulb doesn't care which way power is fed to it, the original power wire to the globe has cut through on the shitty globe holder (has a sharp edge on it where the wires enter) and now you are using the wire which hasn't been cut and the other wire is now the earth and it dioesn't care where it gets its earth from

[Frank]

If all you have done is swop the wires over at the bulb holder and the fault is now cleared then the problem can't be with the wiring because they are still the same polarity with respect to the battery. The fault must lie between the old earth terminal on the bulb holder and the bulb filament. I suspect high resistance either in the holder or bulb itself. Changing the wires over puts the +ve through that section which is more forgiving than an earth fault.

[Norm]

Frank, nothing to do with polarity, it is the fact it is now earthing out on the wire AFTER it has passed through the bulb