4 headlight mod

[chuck16]

Wow, that makes it look easy enough. I might just have to try it. Good find Walbern.

[chuckwi11]

How much differnet/more difficult is the mod for 2003/04 Silverados?

[silveradoman]

Ah!! of course! positive is always fed through the switch, high beam negative is the control circuit for the low beam, thanks a lot!

[FirehawkNS]

Good stuff guys!!! Thanks!!

[walbern1]

Apparently the 03/04 have gone back to a standard "switched positive" instead of a "switched negative" like the 99-02 but I'm not entirely sure. I'll check around and see what I can find.

[walbern1]

This is a cut and paste from another site but all the feed back seems positive

Keep in mind this is on a 2003 GMC - other years may be different, even 2003 chevrolet may be differant although I would think it would be the same. For all lights on with high beams:

The bcm is under the steering column, I had to remove the dash panel to get to it. There are 3 larger 24 or so pin connectors on it. The one I am referring to is the 24 pin on the left side.

This connector has 2 rows of 12 pins, one above the other. There are pin numbers associated with them but they were hard to read so I'll explain it like this:

Top row: 1 2 3 4 5 6 7 8 9 10 11 12 -we'll call T

Bottom row: 1 2 3 4 5 6 7 8 9 10 11 12 -we'll call B

T1 is black-white and is High beam control- tap into this and solder a diode with the band ends towards the T1 wire. I used 1n4005 diodes. Now for the other end of the diode you will solder a short length of wire on and tap into B4- it's pink and is the low beam control.

When you're done make sure to insulate the ends of the diode and wire and everything else. Start the truck,turn the headlights on if it's not dark, you're low beams should work as normal. Flip to high beam and everything should come on. All we're really doing here is operating the relays under the hood that turn these lamps on normally. There should be no problem with power as they are still getting power the factory way. My only concern is the grounds on the headlamps, I'm hoping they don't run too warm running both lamps at once, and I don't know if both lamps are grounded together or if they have individual grounds. I may have to upgrade the grounds if they give trouble. Hope this is somewhat understandable!

Further note- if you are testing with the ignition switch off the DRLs will not come on at all, that's why I said start you're truck in the testing.

[chuck16]

Cool and all but, that looks like a lot more work than just sneaking in under the Electrical Center...

[FirehawkNS]

Originally Posted by walbern1

1) Open hood

2) Remove brace from firewall to Driver's side fender.

3) remove top of Circuit panel

4) unhook the snaps from the passenger and drivers side of the cover...look hard they are there!

5) Roll entire circuit board over towards the passenger side.

6) Locate the Grey connector...there is only one.

7) at location D3 (3rd down 4th to the right) is a light gauge yellow wire. It is the only yellow wire in this row.

8) Tap this wire and ground it to the Light ground on the firewall. Follow the lead from the Hood mounted light, and you will find it ...just to the left (YOUR OTHER LEFT!!!) of the Master Cylinder.

9) Put your stuff back together...you are done...arent you glad you kept that cover?

Enjoy your new quad headlights!

I cut and pasted this from another forum but have done this and it works great. There is another way to do it using a relay but this is alot easier and since your working on the power side and not the dround you don't need a fuse. The lights themselves are fused on the power side of the circuit

This worked great. Just got finished doing it. THanks a lot!!


Do you think it would be the same on a 2004? Got a buddy that I would like to do this for as well. I guess it would be a matter of looking to see if it is the same setup!!

[walbern1]

No. 03-04 are different look at the post I made above on this page.

[FirehawkNS]

Sorry, I saw it the other day and forgot!!

Thanks!!

[chuck16]

Just did the mod and it's super easy; took me all of 20 min. Thanks again Walbern. So, far so good, this truck has been a real treat to work on.

Thanks!!!

[walbern1]

Which way did you do it Chuck? Just so everyone else knows which ones work.

[chuck16]

This is the way I did it; it took no time at all.


Originally Posted by walbern1
1) Open hood

2) Remove brace from firewall to Driver's side fender.

3) remove top of Circuit panel

4) unhook the snaps from the passenger and drivers side of the cover...look hard they are there!

5) Roll entire circuit board over towards the passenger side.

6) Locate the Grey connector...there is only one.

7) at location D3 (3rd down 4th to the right) is a light gauge yellow wire. It is the only yellow wire in this row.

8) Tap this wire and ground it to the Light ground on the firewall. Follow the lead from the Hood mounted light, and you will find it ...just to the left (YOUR OTHER LEFT!!!) of the Master Cylinder.

9) Put your stuff back together...you are done...arent you glad you kept that cover?

Enjoy your new quad headlights!

[FirehawkNS]

Same way I did it!!

[jsalaki]

my 00 headlights have quit working problems is in the ground wire feeding the brite and dim sw. does anyone know what color this wire is and where it grounds? thanks for any help