Okay, I've searched and seen just about every possible combination of lights coming on and off with various switches, but I have yet to find what I'm looking for.

I have a set of Hella 450 driving lights, to be mounted in the air dam. What I would like is for these lights to come on with the high beams. I don't want to change a thing about the fog lights, which seems to be what most people here do.

It SEEMS like it should be quite easy, and just a matter of tapping one of the wires that goes into the headlights. From my reading I'm now not sure if it will be that simple, but let's assume it is for a moment. There are three wires going into the main headlight. One is solid red, one is blue and white, and the third is yellow and red. What I'm hoping is that one of these controls the high beams, and I can simply tap into that wire with the supplied inline connector. Please let me know which wire to tap, or if I'm out of luck and need to go a different route.

Thanks,

Phil

The blue/white is the common positive, and the red is the switched ground for high beam.

Use the wires IDed by Mulder to trigger a relay, feed the relay (w/ an in-line fuse) from the alternator positive, run the power out of the relay to the driving light, and then run the ground from the driving light back to the neg. terminal on the battery. If you just run power from the high beam wires to the driving lights you'll overload the headlight circuit even more than it is now.

While you're at it, convert the headlights over to relays and you're headlights will be about 25% brighter.

While you're at it, convert the headlights over to relays and you're headlights will be about 25% brighter.

I agree with that one, if more people did this instead of buying aftermarket bulbs of dubious quality and light output they would be better off.

Like you, I've also measured the voltage drop on the ground side (about 1.4 VDC). That, added to the 0.4 VDC drop on the positive side makes for a whooping 1.8 VDC loss between the battery/alternator and the headlight bulb. Given that brightness goes up with the 3.5 power of the ratio of the applied voltage to the design voltage, the difference in light output is huge.

Thanks for the quick replies. Rory, you are obviously good at this stuff and I'm quite new to wiring lights (plenty of stereos, but no lighting stuff), but my Hellas came as part of a kit with all of the wiring, a switch, and a relay. Presumably it will be fine to wire the lights as shown by the schematic? The power for the driving lights comes off the relay, and certainly not directly from the high-beam wire.

Thanks again for the responses.

Phil

The schematic that came with the lights may or may not work. Unless the schematic states that it is for a switched ground system, it probably won't work. In a switched ground system (like is used by Subaru), the power is connected whenever the car's power system is enabled. The light switches supply ground --- disconnect the ground and the lights turn off. Just be sure that you take both the (+) and (-) signals triggering the relay from the wires entering the headlight connector and you'll do fine.

Actually the headlight power is switched. It goes on and off depending on the position of the headlight switch (on with the switch in the second position).
It will also be on when the DRLs are on unless they have been disabled completely by disconnecting the main DRL module.

I haven't really dug into this much, but don't the headlights already use a relay system?

I'm currently considering different options (driving in fog location, driving on bumper, etc). I haven't installed relays before, but I've done other minor electrical stuff myself. It doesn't sound too tough to me. If its pretty easy I may just try doing relays to the stock headlights and see how that leaves me.

tcc

Originally posted by thechickencow
I haven't really dug into this much, but don't the headlights already use a relay system?

Yes, the stock headlights do use relays, but not very well. The advantage you have with relays is that you can minimize the voltage drops in the wire by minimizing the distance between the bulb's filament and the power source (battery / alternator). In Subaru's case, they make good use of a relay for the hot side (it is in the engine compartment, just behind the battery), but they still run the ground all the way back into the cabin to another relay behind the glove box (way to long a wire run if your goal is to keep the voltage drop to a minimum). To compound the problem, they use wimpy wire (16ga?) rather than something like 10-12ga that is called for based on the currents involved.

Wire the Hellas as in the instructions. Connect the blue wire to the yellow-red lowbeam ground (which is positive when the highbeams are on). I did this for my Hella FF300's and it works great.

slightly more detail in:
Driving Light Wiring (http://forums.nasioc.com/forums/showthread.php?s=&threadid=303071&highlight=hella)

ok, i just came up on this thread and have a question.

what exactly do you mean by converting the headlights over to relays...in which they become 25% brighter?

how exactly do you do this? i'm confused hehe...sorry

Any idea's on the rating you should get for the relay's to run them? My subaru's lights are nice and bright as it is right now but i would like to do this to my mustang because there seems to be no difference in lights on or off :D well they are on but they suck.

Originally posted by Phatstud
what exactly do you mean by converting the headlights over to relays...in which they become 25% brighter?

how exactly do you do this? i'm confused hehe...sorry

As explained here the headlights use a common positive, switched ground system. Because the ground wiring runs all the way from the headlights to the switch inside the car, through rather thin wires, there is a substantial voltage drop in this part of the lighting circuit. This results in a loss of light output since the headlights are not receiving full voltage.
The solution we are discussing is to use the switched grounds to control relay coils (one each for low and high beam) rather than power the lights directly. The relay contacts would in turn be used to supply a direct ground to the lights right from the battery, thereby eliminating the loss from the car's wiring.
Does this make sense now?

so i guess i know what you're talking about now.

the current setup wires running from the headlights to the relay is sort of long, plus using thinner guage wires than usual, which means not enough juice running to them?

so how do you convert this now? :)

i'm a little new to all this.

Not exactly. There is no relay on the ground side and that is the problem. The mod is to add relays and use the old wiring to control them.

Originally posted by mulder
There is no relay on the ground side and that is the problem.

There are relays on the ground side, but the way they are used makes the problem even worse. Ground to the headlights is switched through the headlight switch on the steering column. These ground wires are then routed to relays (high beam relay for the high-beam ground and DRL relay for the low beam ground) located near the glovebox. The grounds are then routed back into the engine bay and hence to the lights themselves:

chassis ground -------> headlight switch -------> relay -------> headlight

Yes you're right, there are relays in the circuit. If you look at the wiring diagrams you'll see that the ground wiring does pass through relay contacts. However the actual high-low switching to ground is done with the headlight switch contacts.
The relays are there to allow the DRLs to work and also to lock the fogs out when the high beams are on. As you said the relays actually make things worse by lengthening the circuit path and adding more contacts for the current to pass through. A direct grounding mod will bypass all that.

edit- ok I just said the same thing you did :p
Should have read your post more carefully. Anyway we're in agreement that this system sucks and can be improved on, especially when you install aftermarket headlights with separate bulbs, at which point the low beams can just be directly grounded and don't even need a relay.

i'm a bit lost reading this. so the ground goes all the way in the cabin behind the glove box, then to the drl? where woudl you wire the two ground switching relays to bypass all of this? do you use the switched high and low beam grounds to control a relay to directly connect a ground to the headlight? so the wiring would look something like this

cut the high beam ground wire, hook the side coming from the cabin into the 85 terminal? 0V when high beam engaged, so want current flow when 85 is 0V so put the 86 at 12V. if that's right, then the wiring should look like this right?:

85-old high beam switched ground
86-battery 12V with diode across the coil

30-battery ground
87-new high beam ground on headlight


then the same for an additional relay for the low beams?

Originally posted by Eaglesfan2422
85-old high beam switched ground
86-battery 12V with diode across the coil

30-battery ground
87-new high beam ground on headlight


then the same for an additional relay for the low beams?

sounds like that should work. just make sure you put the relay so that both headlights are getting the direct ground and not just one side. or better yet, do one side only so we can get a side by side comparison of the direct ground and the factory routed ground.

will adding relays help with lighting performance of older subarus... ie my MY99 RS?

Nate

Originally posted by NateDogg
will adding relays help with lighting performance of older subarus... ie my MY99 RS?

Nate

don't think it would help much at all because you don't have daytime running lights, do you?

This has been a very informative discussion. But I am new to this, so I would like to know a little more information. Like part numbers and a schematic. I guess I am a graphics oriented type of guy, I need a map for something like this. Also what gauge wire should I use?

On a side note, does any one know about those grounding systems that are out. Where would be good points for something like that.

thanks
RR