Left (driver side) runing/signal light problem

[SoCalE9]

Having problem with the light. When I turn on the headlights, this light won't turn on. It works with the left turn signal. They use the same wires to the bulb. Where do they separate from the running lights and signal lights. Where should I look to troubleshoot? Anybody out there have a suggestion?

SoCalE9
1972 CSi

 

[sfdon]

Nasty little defect in the design of the bulb holder - pull signal cover and inspect round bakelite contact at base of bulb to see if it has worked itself out of the holder. Use epoxy after re-inserting.
Hope this helps...

 

[Arde]

The US version uses dual filament bulbs, so it is likely that one of the bulb filaments is burned, but you may already have checked that.
If the running lights work fine in the rear, then most of the circuit (cable, fuse, switch) is fine and you are down to the bulb holder as suggested by sfdon.