4-HI Headlight mod 03+

[Kenny C]

This is a very easy and cheap mod to do. I think all of the parts needed cost about $3. This mod is done underneath the dashboard of the truck (@ the BCM)...not under the hood. I will try and explain things as simplistically as possible.

Parts needed



1N4004 Rectifier Diodes - 1 Pack


Heat-Shrink Tubing

Remove the duct work on the drivers side floorboard

Before removal


After removal

You should see this black box with the white sticker on it (the BCM)

It's held in by plastic clips. Slide the box towards the rear of the truck to release it from the clips.



Notice the labels on the sticker



Find the gray plug and remove it





Insert the diodes in the pin slots on the top of the plug... use the diagram below to run what ever configuration you want.

This is how my plug looked after diodes were plugged in with heat-shrink around them


I went from B5 to B4 to have lows with constant fogs, and also B4 to T1 to have HI 4 + Fogs
Atomic I borrowed your diagram...I hope you don't mind



It does matter which way the diodes are installed or they will not work...just follow the diagram and you shouldn't have any problems. If it don't work, try the diode the other way.


Test every thing before re-installing
It should look like this...with the high beams on


I had the hood up because I cleaning the engine bay. If you have any questions, I will try and help.

Kenny

[JB]

You did a fine job

[Matts03]

Great write up. As if i need another way to blind people. Ill be doing this soon. Thanks!

Matt

[Kenny C]

Originally Posted by JB

You did a fine job

Thanks...Now come paint my calipers!

Originally Posted by Matts03

Great write up. As if i need another way to blind people. Ill be doing this soon. Thanks!

Thanks man

[blue72camaro]

Thanks man, worked like a charm. I stopped at radioshack on my way home and got the diodes and installed them when I got home. The only difference I will note is that on my 06 HD the box could not slide back to come down. I could however flex the clips on the passenger side that hold it enough to get it to drop down.

Man my truck isnt even a week old and I am already modifying it.

THanks for the write up,
Matt

[blue72camaro]

Well I must have pulled the diode loose from my low beams to fog light when reinstalling the box last night. Did you use anything to secure the diodes in place?

[Kenny C]

Originally Posted by blue72camaro

Well I must have pulled the diode loose from my low beams to fog light when reinstalling the box last night. Did you use anything to secure the diodes in place?

Sorry to hear that man. I just left about 1/2" on either side of the diode sticking out of the heat-shrink. They stay put for me. Did you remove the plug before inserting the diodes? The reason I ask, is that when you remove the plug, the wires are loose on the back of the plug, but tighten back up when the plug is re-installed. If you get the diodes into the sockets far enough, they should tighten up with the wires.

EDIT: Are you highs and lows still working together?

[blue72camaro]

Yeah I put them in with the plug undone and the high lows are still working fine. Some unsuspecting person in front of me was the test dummy to see if they were working or not.

Still cant beat this mod. I think I have $.83 in the diodes to do this and I have a roll of heat shrink for wiring up my camaro when that time comes.


On a side note what all did you do to be able to paint your bumper pad and air dam to match? and who makes the clear lenses?

[Kenny C]

Originally Posted by blue72camaro

On a side note what all did you do to be able to paint your bumper pad and air dam to match? and who makes the clear lenses?

The bumper pad comes painted on 06' trucks, and I didn't paint the air dam. They also changed it on the 06' models to almost smooth black, from textured gray. Clear lenses?? All of my lighting is stock, except for the bulbs. I have Silverstar high/low bulbs and regular 3157LLA for the DRLs and parking lights. Wish I could be more help on the parts list Keep us posted on getting your lights working though.

[blue72camaro]

I see, my 06 2500hd has orange reflectors on the outside corners and the bumper pad is textured black plastic. I didnt realize that the 1/2 tons were different.

I will let you know what I find on the fog lights tonight.

[Kenny C]

Originally Posted by blue72camaro

I see, my 06 2500hd has orange reflectors on the outside corners and the bumper pad is textured black plastic. I didnt realize that the 1/2 tons were different.

I will let you know what I find on the fog lights tonight.

In my sig, I unsaturated the pic of my front end in photo shop to make it black and white. I also unsaturated and motion blurred the main background. The profile shot of the truck is in color with the wheels blurred. My reflectors are amber. I didn't know the HD came with a different bumper cap either?



Since this pic, I have color matched the bow tie, but the rest is the same.

[JB]

Yes the 2500HD's have a taller bumper cap and they dont come painted.

[blue72camaro]

Alright well I am not real sure what the problem was exactly. I think it was just a loose connection. But after my first attempt at fixing the problem I somehow managed to completely dissable the fog lights. How I am not sure. I then pulled both diodes out and they were still disabled. I pulled the fuse under the hood and it was fine so I reinstalled it and magically they worked again. So I reinstalled the diodes and got them working again. WHen I went to put the box back up I knocked the high-low diode out the this time so back down it came agian. I reinstalled it and then very carefully put the box back up making sure not hit the wires on on the dash as I went.

Anyways the mod does work just becareful to hit the right holes with the diode wires and not to hit them on things under the dash when reinstalling the electrical box.

[JB]

I put my diodes under the fuse box lid directly to the relays...much easier on the back/neck
I did mine that way before I knew about Kennys method

[Kenny C]

Originally Posted by JB

I put my diodes under the fuse box lid directly to the relays...much easier on the back/neck
I did mine that way before I knew about Kennys method

Now you tell me

[Kenny C]

Originally Posted by blue72camaro

Anyways the mod does work just becareful to hit the right holes with the diode wires and not to hit them on things under the dash when reinstalling the electrical box.

Sorry to hear your having trouble with the diodes staying put. Mine stay where ever I put them

[blue72camaro]

JB, do you have a diagram of where to put them on the fuse box? If mine give me any more trouble I may move them to out there.

I think the reason That I knocked them loose reinstalling is that I smacked them on the backside of the dash and dash support putting the box in the one time. It got bound up and when it came loose I hit the box on the dash pretty hard.

[JB]

Theres a thread on here somewhere that has all the info with diagram...I searched but couldnt find it.

[Kenny C]

Originally Posted by JB

Theres a thread on here somewhere that has all the info with diagram...I searched but couldnt find it.

This one...http://www.fullsizechevy.com/forums/showthread.php?t=184028&highlight=4hi+headlight+mo d?

I read alot of complaints about doing it this way and chit shortin' out. What ever works

[JB]

Originally Posted by Kenny C

This one...http://www.fullsizechevy.com/forums/showthread.php?t=184028&highlight=4hi+headlight+mo d?

I read alot of complaints about doing it this way and chit shortin' out. What ever works

Like installing them under the dash is any different electrically?

Mine looks much nicer and dressed in than the picture shown. I have had mine like that for 11months and I havent had one single problem. I used to work on computer based land aquistion modules for Haliburton Geo so wiring little stuff like this is childs play to me.