Any help is appreciated, I am scratching my head for this.

I built a headlight relay harness with cheap components to be able to trigger my LED driving lights with my highbeams. I didn't understand the negative switching aspect of the factory headlight harness when I built it, but it did work. Low beams worked, highbeams worked, was able to toggle an added switch to allow a 3rd relay to trigger off the highbeam relay for my auxiliaries.

In May, I ended up replacing my driver side headlight. So I took the opportunity to swap out my headlight bulbs in both because they had about 8 months on them, and typically don't last more than 9-10. While aiming, I switched the headlight stalk switch forward, and realized that I had a problem: My highbeam filaments were illuminated, but the lowbeam filament was still energized.

I checked over my relay harness, looking for chafed wires, swapped the relays all around to see if the issue changed. Thinking that my cheap relays that did not have fly-back diodes/resistors had damaged the stalk switch contact points, allowing some voltage to leak/arc between the high/lowbeam contacts, I ordered and installed a replacement switch. No change in behavior.

I ended up taking the neg switched lowbeam and highbeam male prongs out of my relay harness plug and swapping them, so that the issue became the opposite.

At that point I had:
-Headlight switch "on" - lowbeam only
-Headlight switch pushed forward - highbeam only ( and auxiliaries, if switched on)
-Pull highbeam switch back to low beam position - auxiliaries remain lit, highbeam filament remains lit, lowbeam relay closes energizing lowbeam.

So for the past few months I have been manually rotating the headlight stalk to turn the headlights completely "OFF" before pulling the stalk switch back to the low beam position and turning the switch back on. Takes me 1/2 a second.

I recently bought a Very nice relay harness from headlightservices . com, great thing, but, I am back to my original issue: lowbeams remain lit when highbeams are switched to.

I am getting about 6.5-6.6V across the lowbeam female factory harness plug on both driver and passenger plugs, when the highbeam is switched on, which is enough to keep the lowbeam circuit relay triggered and the lowbeam circuit energized through the relay.

Has anyone had a similar issue? I've been digging through the forum/googling and I see lots of issues with the DRL modules on '00 and later models, but none of the threads I have come across have anything about the low beam side of the harness remaining energized when the high beam side is switched over too.

The problem/issue here is that the high beam indicator bulb in the cluster is powered through the low-beam filament in the stock wiring. The current flowing through the high beam indicator bulb is holding a relay on, but isn't quite enough to turn the relay on in the first place (switching current vs. hold current) - thus the odd behavior. Have you noticed your high beam indicator glows dimly in certain circumstances? (that's your clue)

Swap your wiring back to the original configuration (on the harness) and load the low beam side of the OEM wiring with some resistance. I think I used a pair of 25 ohm resistors (just get some LED bulb load resistors and wire those in).

-Charlie

Could I just pull the highbeam indicator bulb to solve this issue then?

My high beam indicator has not worked with either of these harnesses, and, again I did not have this issue with the first harness originally, it began to occur at some point and I noticed it a few months ago.

Pulling the indicator bulb might work... And putting in the right load resistance in the right place would work too (and probably get your indicator back working).

-Charlie

Ok. Picked up a pair of resistors. Do I need to run them in line between the lowbeam pin on the relay harness plug and the lowbeam relay, or between the lowbeam pin and chassis/ground?

You want them hooked up as if they were the factory low beam filament (you probably have one factory H4 plug sitting there unused - shove them in there for a test)

-Charlie

Well, I wired a pair of LED resistors across the lowbeam passenger side headlight plug, and it all works correctly now. I appreciate the help man.