12-28-09.

Oh it's going to be a late night.  Just did the electric fan page, the last is this page!  Do you have crappy 510 headlights?  One bright, one dim, bright lights where one works and you get a three light mess?  Here's how to fix it.

This is where the headlights and alternator end up for grounding, as mentioned in the photo.  Also, take care of your corrosion while you're at it.  It's embarassing.

This is where your headlight relay is located.  You'll need to probe incoming power off this connector and ground it to the two black wires on the same connector.  Use the strut tower ground first, see how many volts you're getting, then try it through the connector.  You should get the same voltage.  If not, you have a ground issue somewhere.

Regarding the dim low beam light.

What happens is one of the low beams is dim, the other bright.  My left was dim, and the right side bright.  So I kept going nuts on the dim side, trying to figure out why.  Also, my high beam lights were barely energizing.  The filaments were glowing orange on both, but not illuminating.  Since I'm not a wiring genius, that threw me for a bit.  I finally got so annoyed that I just disconnected the bright right side headlight and reconnected it, which re-established a ground connection and fixed it. 

The reason is the right headlight actually had the crappy ground, and since the ground is shared on Datsun 4 headlight systems, it had snaked over through both high beams, to borrow the ground off the low beam.  Thus, one really bright right side, and a dim left side.  Freakin' weird, I know.  Anyway, after this, the high beams worked correctly, and the low beams.

I also replaced the headlight switch, though I won't write about that here as I'm not pleased with the fitment.  It works fine, just doesn't look all that good in the old spot.  The stem isn't nearly as long, so you have to grind off some of the button and enlarge the hole on the dash plate where it fits through.

The short of it is, check all your headlight connectors and probe some grounds.  It's so much nicer when it works!

What high beams should look like.  While you're in there, put a ground strap from the block to the frame/body.  I ran one from the front motor yanking bracket to the same ground that the alternator/headlights use.  Bolts right to the strut tower.