Head lamp Problems????

[mikesgmc68]

I have a 68 Gmc half ton long bed p/u. I pull my light switch and I have running lights, no sides markers work, but the frt and back running lamps work. The directionals works but no headlights work. I put in a new headlamp switch and the high/low switch. Fuses ok. What else could it be. I am a oldsmobile guy and new to this truck thing. Any help would be greatly appreciated. Thanks.

[69TowRig]

Does your '68 have side marker harnesses? That was optional back then. My '69 doesn't have the harness, so the markers don't work. It became standard in '70.

Check the ground for the headlamp circuit, use an DVOM and see if you have voltage getting to the bulbs or not.

[VetteVet]

If you go to the electrical forum and click on the wiring diagram sticky and scroll down you'll find some colored wiring diagrams that may be some help.

[mikesgmc68]

Thanks, I'll check these out.

[70c10]

Make sure you have a good ground on top of the passenger side core support. Take that bolt out and scuff up the metal on the core support and put the bolt back in.

[boundstaffpress]

The red wire that comes to the headlamp switch only powers the headlights, the orange wire powers everything else. If you don't have lights, check the red wire for power. Use your ohmmeter to check your new switch. With the nob pulled all the way out, you should have a circuit from the red connection to the blue connection (power out to the headlights).

Next check your dimmer switch to see if you have power to and power from. I had a bum dimmer switch, but it was from being burried under manure for 5+ years.

You can click on the links on my signature for wiring diagrams, or send me a PM for a 300 DPI version.

[mikesgmc68]

Thanks for the info.