Sorry I haven't read though all the dialog between you guys - I know gregz is another car guy. I'm only going to shed a little in put on my experience installing HID bulbs for my headlights which would inturn be similar to you DTRL.
- bought cheap set, ballasts and bulbs online and installed.
- started driving and people were pulling over out of my way, apparently a ford five hundred would have made a good under cover cop car
- quickly realized THAT is what is going to get me pulled over by a cop and because it simulates an emergency vehicle, it has tickets and vehicle inspections written all over it - trust me I've had my experience with what gets their attention
- looked into it, and when in daytime, your headlights get a low voltage as they get a inconsistent voltage or something (its been years since I've done this so pardon if I'm wrong) and thus causes the ballasts to get a inconsistent signal to be on....or off.
- There are "anti flicker" relays that you install between you stock wiring harness and the HID ballast (provided you haven't done mods) which prevent the flicker
- I've installed these.....they work
- Just a general read of what I hear you want to do.... sounds like some modification of the stock wiring or addition, If you not really good at it... I always recommend leaving it to someone that is. Your lights not working when its pitch black going through the mountain one time because if it.... wont be cool at all.
To give you an example, I've re-wired a street / strip car with all new wiring - I'm very comfortable with the 12v system on anything pre-early 90's. Its just my mechanical and wiring intuition (not my experience) that the newer cars rely on their wiring circuits so much.... that I try to avoid doing to much to them

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1.) However if you REALLY wanted to add LED driving lights (I've wanted to do this for my own fog lights using say..(6) Cree XM-L2 chips per side (just shy of around 1200 lumens each = 7200 lumens which is almost 3 times more lumens than a head light bulb).
2.) Tap a wire into the existing harness (positive) that goes to your current driving light / fog light) in a way that it would be easy to undo (I always solder)
3.) Take a bosch relay you can get from Lordco and run that "trigger wire" to terminal (86) on the relay - this is the trigger wire to turn the relay on / off
4.) then run a wire from terminal (87a or 87) to your lights to complete that circuit
5.) The headlights should then be independently grounded
6.) Supply independent 12v to the relay, in the most extreme case you would run a 10 ga wire (I believe thicker is better when it comes to headlights) and the most extreme case, battery terminal or alternator post, to the relay post (30/51)
7.) I encourage there to be a fuseable link, or fused section between this circut (20amp max)
Note - double check those number because I suspect I'm partially wrong.....its been about ten years since I've worked with that relay and it confuse me until I start playing with one (before installing) so DOUBLE CHECK and confirm those terminals before installing.
if this explanation was already given, I apologize... its morning...I'm not a morning person.... and it just reinforces what you could do then
Also note LED prefer a stable voltage source... not a varying voltage that cars would offer (range from say 12v to 14.4 volts depending on condition of charging system, RPM ) so I recall seeing another little relay type thing that promotes a limiting voltage of 12V or so. From what I would interpret this would just ensure your LEDS wouldn't get brighter as you say accelerated from a stop.... or dimmed as you came to a stop (that's what I would consider a poor installation) - it would also probably enhance the LED life and run them at a voltage they like and temperature.
As you might see... I like 12v systems and at least pretend to know what I'm talking about
