Headlight and marker lights not working together.

2007 Freightliner Century Class S/T. The headlight and the marker lights will not work together. The headlight switch is down for marker lights and up for headlight and marker light together. When I push the switch down the marker lights work as they should. I push the switch up and the marker lights go out and the headlights come on. I replaced the headlight switch and that did not fit the problem. Talked with Freightliner and they said that the interrupt switch was bad. Replaced the interrupt switch and that did not fix the problem. I also replaced the relays for the lights and no help either.

Has anyone ran across this before? Or does someone have a schematic for the wiring?
I found that site as well but was only able to find the fuse / relay panel diagram. Or I was not smart enough to use the site. I need a true wiring schematic.
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Alright after pulling half my hair out I have found that the 87 pole on the marker light relay is not getting power. it should be getting power all the time. I can put a hot jumper wire to the 87 pole and everything works perfect. This fuse panel does not have individual wires going to the each fuse and relay. it is an enclosed unit. I am guessing it is a circuit panel not sure. Going to do a couple more checks but looks like the fuse panel is getting power to all the places it should so at this point I am assuming that the fuse panel has an internal problem.


Instigateur №166™
Crap like that is so fun to chase down! Not


Well-Known Member
Sounds like those lights need a team building exercise. Maybe then they'll learn to work together.


Professional Pot-Stirrer
Jump power to where it needs to go. If it goes around a fuse, get an in-line fuse holder and use that for the jumper.