I am doing one of the oh-so controversial HID retrofits - I got myself I nice pair of projectors and bulbs (I am using cheep ballasts until I have the money for some nice OEM ones). The projectors I bought have solenoids to open up the high beam. I would like to use the lights with my Jeep's current light switch on the steering column. My halogen lights are h4 and the low beams are not on when the high beams are. If I want to wire a bi-xenon solenoid I will need to find some way of getting the light to stay on and have the solenoid open when the high beam is on.

I have an idea that will work, but it involves a relay which means the lights will momentarily be off when I switch from low to high beam (as the relay changes from closed to open). Here is my drawing, will this be good enough, or will I need to make sure the voltage does not get cutoff when opening the solenoids? enter image description here

1 Answer 1


Cycling HID lamps the way you propose will reduce the lifespan of the bulbs, they aren't made to be turned back on shortly after being turned off.

Also, I'm having trouble making sense of your schematic - the oval labeled "LIGHTS" - is that supposed to represent the ballast? I don't know that I'd power that directly from your H4, seems like I'd want a new fused run from the battery through a relay powering the ballasts.

I am not affiliated with them, but http://www.theretrofitsource.com/ sells kits that comes with a ballast controller module that can be interfaced directly to your factory H4 connector. I have one in my Subaru. It takes care of the things you appear to be overlooking - like keeping the ballast and bulbs powered while switching from low to high beams (on HID's all that should happen is the solenoid to move the shield should be powered), or implementing a time-delay so that the ballast does not fire, die, and fire again in rapid succession while turning the key from off through accessory to run, temporarily to start, and back to run.

  • The connector labeled "lights" is the ballast. I wasn't sure if the momentary switch between open and close would be too long.
    – Sponge Bob
    Dec 25, 2012 at 5:31
  • Long or short (and it will be short), it's still causing a hot re-strike which will shorten your bulb life (can't find any solid info on how much, but know that all factory systems implement measures to avoid hot re-strikes). Dec 26, 2012 at 15:15
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    Might be able to use a capacitor there to keep the circuit hot over a short switch over though I much like the prebuild solution.
    – Rig
    Dec 29, 2012 at 4:12
  • The site I linked to, I think they will sell just the wiring harness and ballast controller module. If it's not in their online store you can probably just email them, @KeeganMcCarthy worth it imho. Dec 31, 2012 at 16:37
  • @Rig I thought about a cap, too. But I think I'll just get one of the harnesses that qes is talking about. Even though they are pretty expensive they aren't much more than building two of the ones I drew out, above.
    – Sponge Bob
    Jan 1, 2013 at 2:06

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