ARB Headlight Harness Problems

I hesitated so long to publish this writeup because there is a small flaw in the configuration of the wiring if you have factory fog lights. With the harness installed and the fog lights turned on, if you turn your lights on with the low beams active, then go to hi beams and back to low, all of the lighting elements in the bulbs will stay illuminated. Essentially giving you the light output of 4 headlights. While this is good for your visibility, it will cause your lights to burn out in short order.

If you take a look at your stock driver’s side H4 headlight plug, you’ll see not 1 but 2 wires connected to the hi beam terminal.

This wire is used to tell the XJ that the hi beams are on/off and allows the fog lights to operate accordingly. The law states that fog lights can only operate when the low beams are on. This connection sends a current through the system that makes its way back into the new harness and keeps the hi beam relay connected when it shouldn’t. If you cut the lights off and back on again, everything operates normally.

I searched around for a simple fix to this but I never found one that I was comfortable with. My fix was to pull the fog light relay from the PDC under the hood. This will keep the feedback from happening but it also takes away your fog lights. This hasn’t been an issue though because I have plenty of light output from the brighter light.

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