2nd Gen Non-Engine/Transmission Sport Headlight Wiring in 2002 2500

[CJ Lagos]

I spent a full weekend building the sport headlight wiring harness for my truck. I hope some of my notes will help someone with the conversion.



My 2002 truck is switched ground, so the lights have constant +12v and the computer switches ground on and off to complete the circuit. It is backwards from most auto electrical systems and threw me for a few loops along the way.



I started by running two power wires directly off the battery through inline fuses to the right and left headlight areas. I ran two wires off each lead that run to the individual headlight sockets. The 9004 power pin is A(right) and the 9007 is B(center).



Next, I cut off the factory driver's side headlight plug and extended the wires to my relays. I used one for low beams and one for high beams.



*The factory 12v(violet wire) connects to relay pins 86(+12v).



*The factory low and high ground wires(low violet/white, high red/orange) connect to relay pins 85(coil grounds).



*Connect relay pins 30(common) directly to a chassis ground(factory sheetmetal screw next to clutch master cyl).



*Relay Pins 87(normaly open) are connected to new wiring running to the the low beam amd high beam grounds in the headlight sockets.



This method lights all 4 filaments on both low and high beams. For good measure, I installed a jumper on the 9004 low beam ground wires that allow me to disconnect inside low beams in the event I want the lights to operate like factory.



This could be a plug and play system with a male 9004 plug to connect to the factory wiring. I was going to order this but ended up splicing the wires instead. The passenger side factory plug is left unplugged and I pulled the fuse.

 

[Thomas]

... and the computer switches ground on and off to complete the circuit...

In the interest of accuracy, there is no computer involved. The connection to ground model years 1999-2002 is through the headlight switch. Also, there is a slight difference in the wiring of the passenger-side bulb socket vs. the driver-side socket for these model years. The basic OEM non-Sport headlamp circuit can be seen here: https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=15712&width=4

I gather from your description that you didn't wire so that the low beams burn with the high beams (the Brite-Box effect). I did. After six or so months I cut the power to the inboard (9004) low beam filaments. I noticed that the reflector adjacent to each inboard bulb was starting to discolor at the base of each bulb. The Sport lamp reflectors are not designed to reflect light (or heat) from the inboard low beam filaments. Burning all eight filaments when high beams were selected was more than the lamps could take. With the inboard low filaments unpowered, I have had no problems in two years running with six filaments burning.

 

[CJ Lagos]

According to my 2002 service manual the factory headlight relay is grounded by the central timer module through the security relay circuit. The CTM energizes the headlamp relay control by internally pulling the cicuit to ground.



The factory wiring is simply used as a trigger to turn my relays on and off. It doesn't matter which side you use.



I wired mine to run all 4 low on low-beam and all 4 high on high-beam. Running new heavy guage wiring to the bulbs helped a lot too.