headlights only one works at a time?

[mspencer]

i have an 1970 1600 and i have not driven it much at all, just picked it up this year not running, and have been working on it. I just completed the paint and installed an AFR gauge to help get it tuned so i am getting excited to start driving it daily. my big current issue is that the headlight only works one at a time, that is, with both the fuse in (10amp) one for each L and R. and i turn on the headlights (pull knob fully out) the PS lights up perfectly but the DS light looks weak or not on. if i pull the DS fuse the PS works perfectly if i replace the fuse on the DS and pull the PS fuse then the DS light works perfectly. i have upgraded the lights to new, but the old lights did the same thing. i checked the voltage at each light when both fuses are on and the voltage is the same at the connectors. so should i be looking at the switch? i don't see where the headlights are grounded in my schematic so not sure where to check the ground but if they both work correctly independently doesn't that mean the grounds are good? any guidance is very welcome.

Thank you.

[Curtis]

https://kendo-usa.org/datsun/datsun_hea ... _69_70.pdf