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Headlight wiring?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Strahan, Feb 12, 2002.

  1. Strahan

    Strahan 1/2 ton status

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    Hullo. I'm in the process of converting my 83 Jimmy from sealed beam to composite H4 headlights. I picked up 4 convertors for $14 apiece. The low beams went smooth as silk, the factory harness plugged right into the H4 bulb but the high beams are missing a prong. Also I noticed that wires go to all three prongs on the low beam.

    I'm a little confuzzed.. being that I have 4 bulbs, I figured it's 4 single filament (2 hi/2 lo) and that since the H4 is a 2 filament hi/lo bulb with 3 prongs, that it's prolly one for ground, one for hot low beam and one for hot hi beam. If that's the case, why are there wires going to all three prongs on my low beams? I can't seem to find my volt meter so I'm in the dark. Anyone know what the pins on the H4 bulbs are looking for as far as +/-? Thanks.
     
  2. Strahan

    Strahan 1/2 ton status

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    BTW, this is how it looks. The pic doesn't really show it that well, but the H4 is on the left. I got one of the Xenon bulbs, lights up white rather than yellow. Works nicely, you can sorta see it's more white than the yellow original sealed beam on the right.

    <a target="_blank" href=http://www.blazer4x4.com/h4.jpg>http://www.blazer4x4.com/h4.jpg</a>
     
  3. Burbinator

    Burbinator 1/2 ton status

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    The "low beams" (top L/R) are dual filament lamps. The "hi beams" (bottom L/R) are single filament (in sealed beams) and turn on only when hi beam is selected, causing all four lights to illuminate. The "low beams" illuminate their second filament when "hi" is selected. That would be why the "low" lights have 3 wires going to them and the "hi" have only 2. You're only using one of the two filaments for the hi's.

    Hope that helps!

    Haze gray and underway...<font color=blue>or blue, in my case.</font color=blue>
    <a target="_blank" href=http://community.webshots.com/user/abshort>U.S.S. Nimitz II</a>
     
  4. Burbinator

    Burbinator 1/2 ton status

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    Too bad they don't make those for my '91...sure would be nice to be able to replace the bulb only and not the whole assembly!

    Looks good!

    Haze gray and underway...<font color=blue>or blue, in my case.</font color=blue>
    <a target="_blank" href=http://community.webshots.com/user/abshort>U.S.S. Nimitz II</a>
     
  5. Strahan

    Strahan 1/2 ton status

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    Ahhh thanks, cool. Maybe I can get away with just bending the extra pin back for the highs. Actually, my intent is to ultimately convert to your style. I prefer that look, but I figure until I get around to it I'll try to spruce up the originals heh. Thanks again :)
     
  6. Burbinator

    Burbinator 1/2 ton status

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    Just make sure the filament you use for the hi beam is the LARGER of the two H4 filaments(small=low, large=hi). It's a readily visible difference.

    Good luck!

    Haze gray and underway...<font color=blue>or blue, in my case.</font color=blue>
    <a target="_blank" href=http://community.webshots.com/user/abshort>U.S.S. Nimitz II</a>
     
  7. dysphemism

    dysphemism 1/2 ton status

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    this isn't all that relevant but ya the 91 front ends are sweet. I converted my 86 to the 91 GMC grille and it looks pretty slick.

    1986 GMC Jimmy 6" springs 3" body, 38/15.5/15 Swampers, 14-bolt FF rear, Dana 60 front, 1991 front-end.
     
  8. Strahan

    Strahan 1/2 ton status

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    Welp, I went to a junkyard and couldn't find a harness to fit the H4 so I just left the original in there for now and buttoned it up. Weird side effect.. the H4 low beam must have messed with the truck's mind, cuz now in low beam mode the H4s are nice and bright but the orig highs are on, but they're dim. When you hit hi beams, the H4s go dim and the orig highs get bright. Very odd. I guess I'll just chop all four harness ends off and rewire it.

    I figure since the H4s are dual filament when I'm in low beam mode I want the low beam H4 filament in the low beam lens to light. When I hit high beam though I want all four H4s firing up both of their filaments ;)
     
  9. Strahan

    Strahan 1/2 ton status

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    Cool. Did you just have to buy a grill and the headlight hardware or did you also need to replace the radiator support and stuff?
     
  10. Innerpiece

    Innerpiece 1/2 ton status

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    just for grins -- I bought 4 dual filiment halogen lamps ... and after a little wiring work I now have all 4 lamps burning low beam and all 4 lamps burning high beam ... It was really an appreciable difference!
     

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