got Multimeter? [aka: volt- ohm meter]
1] Pull the lenses, check both bulbs for continuity. If not have, replace bulb (can test bulb by direct patch to B+ and B- if you want. Keep those wires separate, ya know?).
2] Check for voltage. If not have, trace and fix.
3] If have bulbs good and voltage, check for ground. If not have, trace and fix.
4] If have bulbs good, voltage, and ground... that's all there is.
5] scrounge live chicken and/ or virgin (live is more legal -ish), sacrifice. Worth a shot, ya know?
Electrical troubleshooting is very very simple, BUT you have to be complete, and precise.
6] Buy "Church of the Free Electron" bible, contact TBerk.
More seriously; if ALL the running rights are out, that'll be a secondary circuit coming off the light switch, you'll need the Bentley manual for reference to electrical schematics. Running lights are Key/on or Key/off, headlights are Key/on only. So if you have headlights but no running lights, X marks the spot.
One circuit brings up headlights, another circuit brings up running lights. Follow me? Find where they meet and you've likely found your problem.
Too late tonight, but I can go look at my Bentley tom'ro and see what I find.