I took care of that "feature" which kills the low beams when the highs come on. it was pretty simple to fix. I looked through my service manual and found the wires which run to the fuse box for the lows and highs before they split off through 10A fuses and to the respective bulbs. I wired a 30A relay to the circuit which is hot when the high beams are on and connected the contact to a 20A fused source and then to the low beam common wire. now when I flip on the highs I have all 4 lights on and functioning. Just to be on the safe side since I like in car-**** Virginia I left the fuse where I could easily get at it to disable the mod for inspection time, because I'm sure they would love to fail me for it. next I need to tackle the fog lights, yet another wonderful feature that I don't care to have on my car!

 

you should post a "how-to" for those who might want to do the same thing while the mod is still fresh in your mind.

 

Indeed. I just picked up an '06 Scion tC for my daughter to drive back to college and noticed that the low beams stay on with the highs. I wonder if the PO of THAT car performed a similar mod. I'd love for my C5 to be like that. In a pleasant case of serendipity, the Scion uses the same headlight bulbs that our C5's use, so I stuck the modded Silverstar 9005's that I had laying around (after removing them for the Toshiba HIR's) in the low beam sockets of the Scion. Sweet...

 

I may do that. I'll probably draw up a wiring diagram for the modification to insert into my service manual. I like to do that when I modify factory wiring at all (even if its only some wire taps and a relay) just for my own future use for diagnostics. I took many pictures during the process also. it took a bit of time since it was the first time I had ever dug into this car's wiring and I wanted to document the whole thing. but it was really a simple mod. what's the best way to upload pictures to this board? looks like they may have to be stored elsewhere...

 

Would be interesting to know what to do.

 

www.photobucket.com is where you need to upload your pics.

 

cool, I'll sign up for an account. does photobucket allow off-site image viewing? I know some of those free sites don't. as long as I can right-click and get the image path to put into a post here that should be good. I have the pics at home, I'll try to get them up there when I get a chance.

 

Yes, they do. Photobucket makes it real easy, they even generate the html tags for you!

 

That's a great fix!

 

it sure is, I can't wait to give it a good trial run. it won't exactly be like having HIDs, but it makes more use out of the stock lights (well, I have silverstar ultras, but pretty much stock)

before I did this sometimes when I Wanted the brights on I just held the flash to pass lever on and its amazing how much more light you get that way than just flipping on the brights in stock form.

I'll see if I can get some pictures of this up tonight.

 

here is the procedure in a nutshell.

remove the negative battery terminal.

remove the under hood electrical center cover, unbolt the electrical center from the frame. looking at the electrical center from the passenger's side of the car, to the right of the B+ terminal on the electrical center is a single nut holding it down. removing this will make it easier to work with. separate the top part of the electrical center (where the fuses are) from the bottom part. There are a total of 4 plastic clips to release. don't pull up too hard on the top of the center there are wires below it which prevent it from moving too far.



Inside the electrical center there is a single wire which feeds one side of two 10A fuses, the fused sides of those fuses run to the two low beam headlights. there is a similar arrangement for the high beams. the idea behind this mod is to use the high beam's signal (before the fuses) to energize a relay. the contact of that relay will be connected to a hot at all times source and the pre-fuse single wire which will turn on both low beam lights. this way when the highs are turned on and the multifunction switch turns off the low beams, this relay will supply the power that the switch is not, keeping the lights on.

tap a wire into the light blue wire feeding the two high beam fuses (check under the electrical center lid to see which ones they are) I had to cut a wire tie to get enough slack to get a tap on this wire.



attach this wire (yellow in my case) to one side of the coil of the relay. connect the other side of the coil to ground. I chose the factory ground point G102 I believe, on the frame rail behind the passenger's side headlights.

on the forward side of the electrical center find the tan colored wire which feeds into the two low beam lights and tap a wire into that. run this wire to one side of the contact of the relay.



Connect the other side of the contact of the relay to the B+ terminal on the electrical center using a large ring terminal the electrical center is open on the bottom, so run the wire down and up inside to make it look neat.



now turning on the high beams will energize the relay which will via its contact supply 12V to the common wire for the low beams turning them both on.



I left plenty of slack in the wires because I hope later to add a second relay to the same trigger and use it to keep the fog lights on as well. As you can see in the picture I added a fuse to the power wire going in to the relay. extra fuses won't hurt anything but its not really needed there since the headlight wires are fused already. I added it mainly so I would have an easy way to pull the fuse and deactivate this modification. if you live in a car hating state, you may need to pull the fuse for inspections. even with the longer leads there is plenty of room below the fuse panel to hide the relay. hide it down there and put everything back together and enjoy being able to see a bit better at night.

 

I decided to add it here since it builds on my previous wiring modification. I also "fixed" my fog lights this afternoon. it was much easier to do than the high beams since I already had the wiring partially done. according to the service manual the fog lights are turned on by the BCM which grounds a wire in the under hood electrical center. this wire energizes a relay which sends power to the fog lights. since I already have a relay which is energized by the high beams coming on it was easy to add a second. I wired up a second relay to the same ground and high beam wires as the first one. with the contacts of this second relay I hooked one side up to ground, and the other side I tapped into the factory wire heading into the Fog lights mini-relay. its the Dark Green/White wire under the electrical center. Now when the high beams are activated the BCM disconnects ground to this wire, and my relay replaces that ground which is taken away keeping the fog lights on with the high beams, the way God intended.

here's the wire tap


the two relays together, one to turn on the low beams with the highs, and the other to turn on the fog lights.


the result, high beams now means MORE light, not less!


side effects:
any time the high beams are on now the fog lights are automatically turned on, so if the headlights are closed you can use the flash to pass feature to flash the fog lights! if you hold the flash high beams lever on when the lights are off they will turn on and pop up, but that's not much of a flash, and you can't do it quickly. now I have something to flash with when the headlights are off. if you have the headlights on and the fog lights off and you flash your high beams, the fog lights will flash with them. this doesn't bother me a bit.
one odd thing I did find, when my modified fog lights are on with the high beams the indicator LED in the fog light button does not illuminate. I'm not sure why as according to the schematics in the service manual that LED is supposed to just monitor the output of the fog lights relay in the under hood electrical center. when my relay energizes the factory relay it should turn the indicator on, but it doesn't...strange!

 

Questions on the fog light mod, if you don't mind.

I actually previously hooked up a relay for the lows on when highs are on, but I used tap connectors to tap the harnesses up front near the headlights near where the main harness meets the headlight harnesses along the fenderwell on the passenger side. Could I then just run a second relay and connect it to the the same high beam and ground wires I already have on the first relay, then somehow locate the fog light power wire and connect that wire to the second relay?

I mean, why would I need to energize the factory fog relay? Is there a reason you did this?

About your flash-to-pass effects. From the factory, with the headlights off, the fog lights light up when you flash. Once I added the relay to keep the lows on when highs are on, that's when my headlights pop-up when I flash. I don't like this. Do you think that the same would happen when you wire in just the fogs to the highs and NOT the lows to the highs?

 

it you just wired the fogs to turn on with the highs it should not cause the headlights to pop up. I'm actually not certain by looking at the service manual wiring diagrams why the headlights pop up when you add the relay to turn on the low beams. so you have done the high/lo mod by wiring a relay into the wires going into the headlight itself and not into the wires under the fuse panel, yet the headlights still pop up? interesting! did you have to use a separate relay for each side or is it just one.

I have heard from others that tried that using a relay to hook up power to the fog light had unintended results. I'm not sure why, but one person on here said that hooking up power to the positive wire to the fog lights resulted in the lights flickering and not coming on as they should. I haven't tried it so I don't know if it was a problem with that particular car or if that would happen with all of them. using the relay to energize the stock fog lights relay retains more of the factory wiring, including the factory fuses. if you added power yourself you would have to have a separate fuse for it which adds to the complexity. plus using the one relay to energize another allows it to all work with a much smaller relay. I used a big 25A relay because I had it on hand, but I could have used a much smaller relay, or even a diode in that case.