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Identifying the pins on the back of a headlight

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by matressking, Nov 18, 2009.

  1. Hi guys,
    I've recently been applying my 5-6 year old electrical knowledge from uni to wiring up a new headlight and gauges on the front end of my sv650. First time i've transferred my knowledge to anything automotive so excuse any ignorance!

    The bulb for the headlight i'm using has 3 terminals (i'm sure that's the wrong word) coming from the back of it.

    1 will be power, 1 will be ground but what's the 3rd?! ...and how do i tell which is which? There are no markings to speak of on or around each of the terminals.

    Note that the high beam is seperate so I can rule out one of them being power for that.

    The headlight is from an xt660 and a link to a wiring diagram is here but it only shows 2 wires connecting to the bulb:


    cheers for the help as always
  2. hmmm...on closer inspection, it seems like there are 2 filaments inside the bulb.

    one is almost all inside a reflector which directs the light straight up, presumably againt another reflector which directs it outwards.

    but, there is also a completely seperate smaller bulb inside the headlight casing too.

    so...one combination of the different filaments/bulbs is high beam, one is low. I doubt you could light both filaments in the main bulb together without it getting too hot so i think that's ruled out of any on the possible configurations.

    i guess i have to figure out which is which.
  3. Usually the two filaments in the bulb are High Beam and low beam. The second smaller globe in the reflector, usually higher up is parking lights required in some countries regulations. These aren't required in Australia but some bikes are still delivered with them.
  4. Generally, the filament inside the reflector arrangement is dip. The reflector in the bulb throws the light into the top of the headlamp reflector, resulting in a beam that slants downwards.

    The open filament will be main, as that is designed to throw light to all parts of the headlamp reflector so as to project a more or less level, focussed beam.

    One pin will be common, one main and one dip. I used to know which was which but I've forgotten and have to work it out from scratch each time.
  5. ah i see, makes sense. cheers guys.

    presumably common is a synonym for ground? why wouldn't they mark them?!?
  6. 'Cos, generally, they're going to be stuck into stock standard holders, which will sort out the "which wire goes where?" question automatically. It's only when folk start modifying things that it really starts to matter whether you can tell or not.
  7. That would be a standard H4 hi/low filiment globe.

    Not 100% sure but I think if you hold the globe with the pins facing towards you (don't touch the glass, it shortens the life of the globe) with the pins in a U shape;
    - The pin across the bottom is the Low Beam.
    - The pin on the left is the High Beam
    - The pin on the right is the common earth return for both.
  8. If you do happen to touch the glass, it can be cleaned with a bit of metho or similar on a soft cloth.
  9. yup i guess that makes sense.

    why can't i touch it? i dont remember but I probably did.

    no meths...vodka?!
  10. The oil in your skin causes the glass to deteriorate and reduces the life of the globe. I don't understand how/why but that's what we all get told??
  11. I don't understand fully either, but I think the glass gets so hot that the oil from your skin burns. I'm not sure why this shortens the life of the globe - maybe it reflects heat back?

  12. I know , I know ... jumping up and down with hand in the air :rofl:

    The oil from your skin etc, makes a "hot" spot on the glass which over minutes/hrs/days etc , depending on the quality of the make weakens the glass to failure.

    Ps, pvda is spot on re the pins. :angel:
  13. Nice one! That was the point of the thread after all!

    Cheers guys.
  14. Aren't I always :-w

  15. sorry to drag up an old thread but no point creating a new one.

    Is it possible to but the "holder" mentioned above seperately?

    I'm sure I could source a part for my sv but does anyone know if I could pick up a generic one in Supercheap or somewhere?
  16. I'm pretty sure I've seen them in SuperCrap with ~100mm wire tails already attached and ready to solder into your existing wiriing. If not, your local auto electrical suppliers will certainly be able to supply.
  17. Cheers Pat.

    What I've done so far is solder wires and then bullet connectors onto the pins themselves but I'm cleaning up the electrics now and would like something a bit more permanent so I'll see if I can find an auto electrics place around.
  18.  Top
  19. 99% of cars use these bulbs, you could score the connector from any wreck on a street near you! If you need to work out the terminals, just apply 12 volts to any pair of terminals. High and low beam will be obvious, if you happen to connect to them both and not the earth, you'll get both filaments glowing dimly (in series at 6 volts each).
    +1 to don't touch the bulb if you do clean with metho.
  20. thanks mate