Sideshow Pob Posted July 10, 2013 Report Share Posted July 10, 2013 Bit of a head scratcher for me, hoping for a bit of advice from those that know. Working on a bike that used to have 2 headlamps, 1 for Hi and t'other for Lo, but now has a single H4 bulb unit. The Hi beam indicator is on when Lo beam is on and I've traced it to the fact that when there is a voltage going to Lo beam, a bit of volts wanders back up the shared negative of the H4 bulb and finds its way, the wrong way, across the Hi beam filament and then down the road to the Hi beam indicator lamp. So my thinking is to put a diode on the Hi beam supply positive to prevent a voltage going back that way. Only thing is I don't know what spec for the diode. Does it need to be 60 watt or just a couple of watt? Ta. Link to comment Share on other sites More sharing options...
2moto Posted July 10, 2013 Report Share Posted July 10, 2013 So, with only the low beam on, is there voltage across the high beam filament? Have you connected both negatives from the previous twin bulb setup to the common negative on the single H4 bulb. Sounds like a ground issue. Link to comment Share on other sites More sharing options...
Sideshow Pob Posted July 10, 2013 Author Report Share Posted July 10, 2013 Unfortunately, I don't have access to the original wiring loom, only the hacked about current stuff. I got hold of 2x 4amp diodes and ran them together in parallel. They get a little bit warm but nothing too bad and it appears to have solved the problem Link to comment Share on other sites More sharing options...
2moto Posted July 10, 2013 Report Share Posted July 10, 2013 I am with Punk. This is not a clever bodge. I would strongly recommend you fix it properly, i.e. figure out the grounding problem. Link to comment Share on other sites More sharing options...
Sideshow Pob Posted July 10, 2013 Author Report Share Posted July 10, 2013 Understand what you are saying, but the diodes are rated at 8 amps not watts so that's considerably higher rating and within spec. I can't return it to the original loom without suggesting to the owner that he converts the single headlamp that he currently has (with an H4 bulb) back to a twin lamp set up that has individual bulb (and therefore grounds) Its the H4 bulb that is the the problem here, I'd never checked continuity of one before, but because of the shared ground you get continuity across low beam and high beam in the bulb. There is nothing to stop a voltage running back down the high beam +ve when the low beam is on. Link to comment Share on other sites More sharing options...
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