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Prevent Low beams from coming on with high beams

Discussion in 'Gen 3 Prius Accessories and Modifications' started by sbddude, Jan 3, 2013.

  1. sbddude

    sbddude Junior Member

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    I have retrofitted HIDs for low beams.The high beams are still the factory halogens. The problem is that when I use the "flash to pass" feature, it flashes the high beams AND the HIDs. This is bad for the HIDs.

    Is there a solution that would only allow the low beams to turn on if they are turned on via the low-beam switch (therefore ignoring short flashes of high beams)?

    I was thinking along the lines of a relay that connects with the parking lights, so that the low beams will only activate with the parking lights on, since the flashed high beams do not turn on the parking light.

    Is there a wiring diagram or info that would show where to find the needed wires to accomplish this?
     
  2. PriusCamper

    PriusCamper Senior Member

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    My eyes hurt just thinking about seeing you doing this in the dark in my rear view mirrors... I'm sure someone will add a solution for you in this post in coming hours....
     
  3. sbddude

    sbddude Junior Member

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    What are you talking about? I don't use high beams behind other drivers at night.
     
  4. PriusCamper

    PriusCamper Senior Member

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    your story triggered a flashback...
     
  5. xliderider

    xliderider Senior Member

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    I think this is all you need:

    [​IMG]

    Your high beam wiring will be stock. Your HIDs will be activated by a relay that is controlled by your parking light positive wire. Therefore, when you turn on your parking lights, your HID low beams come on.

    If you want to be able to turn off your low beams while parking lights are on, then you need to install a switch to override the relay. All you need is an SPDT toggle switch and run two wires through the firewall.

    You probably want to get your power directly from the battery, not from the fuse block (sketched it up fast).
     
  6. xliderider

    xliderider Senior Member

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    When all lights are off, flash to pass will only flash the high beams. Activating the high beams when the parking lights/low beams are on, will give you low beams + high beams. I believe that's what you wanted.

    You can get an HID wiring harness cheap off eBay and put in a relay (if it doesn't already have one).
     
  7. sbddude

    sbddude Junior Member

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    Yep, that's what I want.

    Where are all the wires that need to be tapped?
     
  8. xliderider

    xliderider Senior Member

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    You're only tapping one wire, from the parking light harness. It is the small light at the top of your headlight. You need to figure out which one is positive and which one is ground. Then run two 18 gauge wires through your firewall. Imagine one long wire with one end tapped into the parking light positive wire and the other end activating your relay that controls power to your HID ballasts, with a switch in the middle (in your dashboard).
     
  9. sbddude

    sbddude Junior Member

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    Why not just tap both wires under the hood, using a relay? The coil of the relay would be activated by the parking lights and the switch of the relay would be normally open across the +12v wire going to the low beam.
     
  10. xliderider

    xliderider Senior Member

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    You could do that by eliminating the "optional" SPDT switch in my diagram, but your low beams will always come on with your parking lights.
     
  11. sbddude

    sbddude Junior Member

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    I don't understand why the dash switch needs to be involved. Can I tap the lights using either of the two circuits below:

    [​IMG]

    [​IMG]
     
  12. xliderider

    xliderider Senior Member

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    What switch are you referring to in your diagrams? The headlight switch on your turn signal stalk? That switch only sends a low power signal to your headlight relay in the OEM wiring configuration.
     
  13. sbddude

    sbddude Junior Member

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    I mean the wires that are going directly to the LB/Parking light bulbs, after the factory relay.

    So in my diagram, "switch" could mean "relay" or "12v source".
     
  14. xliderider

    xliderider Senior Member

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    OK, gotcha. Diagram one would work, but you have to reverse the connections at terminal 30 and 87. Terminal 30 is the one you want power to go in, and terminal 87 is the switched terminal going to your low beams.
     
  15. sbddude

    sbddude Junior Member

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    OK, any reason why #2 won't work? (assuming the relay polarity is switched as you mentioned).

    And do you know the physical location of both wires? Are they just behind the headlights?
     
  16. xliderider

    xliderider Senior Member

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    Because I still don't understand diagram #2 lol.

    Use a harness like this:

    HID Conversion Kit Relay Harness H1 H3 H7 H8 H9 H10 H11 9005 9006 880 881 40Amp | eBay

    Here's the harness from the listing:

    [​IMG]

    Then you add another SPST relay for your parking light override/control of your HIDs. You will add the components in the dotted black box in the upper left of the diagram to your HID harness/HID installation.

    [​IMG]

    So, the Low beam control wires (and ground) are as easy as plugging in one of your stock headlight plugs into the HID harness' stock plug. The only connections you need to make are to the battery, chasis ground, and tap into a parking light + wire. Again, the parking light wiring is easily found at the back of the headlight near the top, connected to a bulb holder (the little bulb at the top lol) the ground is usually white with a black stripe, the other wire is the positive wire.

    You really want to use an HID harness that taps power from the battery instead of from the OEM headlight circuit because of the "surge" that occurs when the HIDs initially fire up. This surge can damage the OEM components, which wasn't designed to carry the high voltages associated with HID startup.
     
  17. sbddude

    sbddude Junior Member

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    I already have a harness like that. I just didn't know where to connect the +/- 12V directly to the battery.
     
  18. xliderider

    xliderider Senior Member

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    Sorry, you're going to need someone else to chime in on where to pull "battery" power for your HIDs. I have my 2 65w highbeam bulbs in my DRL mod running off the available terminals in the upper left area of the under hood fuse box and they operate just fine.

    Hopefully someone will say whether this is the place to get your power for the HID relay.

    Edit: I just looked at the parking light wires. One is white, the other is black. So test the voltages, I believe the white wire will be the positive wire.
     
  19. xliderider

    xliderider Senior Member

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    Did a search on this forum. There is a bolt that is securing the main heavy cable that brings in power from the rear hatch mounted battery to the fuse block. It is under a black plastic cover on the left (engine side) of the fuse block (cover lifted away in pic). You can clearly see the bolt head in the middle of the picture to the right of the heavy white wire.

    Be extremely careful with this terminal, it's basically the positive terminal on your battery!

    [​IMG]
     
  20. sfv41901

    sfv41901 Masta S

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    I believe the purpose of this is not for night time use but rather during the day when u use the flash to pass......since the op has HIDs in his low beams, the flashing can damage the ballasts & bulb so he's looking for a way to keep the low beams off with the flash to pass during the day.
     
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