I got this off of another website:
http://www.tlg-auto.com/forum/index.php?topic=3.0
I hope it is of some help. Also there may be a better way, I just happened to come across this. The guys that are better with the electrical systems of our cars may have an even better solution.
Quote from: minnesotaLSfan on February 23, 2011, 08:20:51 AM
I have a 2000 LS with h.i.d.s, and I want the high-beam and low-beam to stay on when highs are in use, can you point me in the right direction of how to put in the diode? And are you using one diode for every light? Or is there one diode for high-beam wire to both sides, and one diode for low-beam wire to both sides?
In order to do this you will have to install a relay for your low beam, on each side, that uses the original incoming power to turn the headlight on to trigger the relay, and the relay gets power directly from the battery.
First, disconnect your battery and cut the headlight wires going to your low beam. Leave enough slack in the wires so you can work with them. It may be necessary to lengthen the wires. Your original headlight wiring, on the vehicle side, would be connected to pins 85 and 86 (It doesn't matter which wire goes to these pins, as long as one is positive and the other is negative)
On the headlight side of the cut wires, ground the wire that should be negative, and connect the positive wire to relay pin #30.
Connect relay pin #87 to the battery with a fuse.
Do this connection with both headlights. Now you will be running straight battery connection wiring to turn on your OEM HID headlights.
Next you have to trigger your new Low beam relays with the high beam trigger. Use a 1-amp diode and connect it to the positive wire of your high beam wiring.
Wire in the diode so that the stripe is facing away from the high beam wiring. The strip should be closer to the low beam relay.
Connect one side of the diode to your positive high beam wiring, and the other side to the positive relay trigger for the low beam.
Now when you turn on your headlights, the relay is powering your low beam. Then when you switch to high beam current is fed through the diode to turn the low beam relay back on again.
Remember to solder and tape up all connections - including the bare diode!