sourcing electrical upgrade parts

[Curtis240Z]

Mike,

Here is what I did.

HEADLIGHT RELAY CONVERSION FOR 1971 240Z.pdf

HEADLIGHT RELAY CONVERSION SPST.pdf

[SteveJ]

How does this circuit look for headlight relays?

I forgot to add a fuse.

I hope you're considering separate fuses for the two headlights. That way, if you lose low beams, you may still have the high beams.

[Mikez73]

Good point. Curtis has provisions to keep the left and right from going out with the same fuse.

[Mikez73]

I hope you're considering separate fuses for the two headlights. That way, if you lose low beams, you may still have the high beams.

Does it matter which way I do that? I could run two wires w/ fuses from battery/alt to the relays or just install the fuses after the one wire separates to go to the relays.

Also it seems like running ground wires from the two headlight plugs would be better...as in the second poic.

[SteveJ]

I suggest separate wires. That way you won't have a splice to split the power.

[pwd]

From the standpoint of electrical noise, it's always a good idea to incorporate a "star" ground. That means gathering all the current return lines into one ground stud aka "the golden spike". That way the variable resistance from corrosion and painted surfaces encountered while carrying the return current through the frame, body shell, etc. is removed. Have you ever heard a click or pop over the radio speaker when you turn on the headlights, or turn signals, or a hum from the ignition coil? This will be eliminated with the star ground, though it takes more wire, adding cost and weight. It should be placed as close to the negative terminal of the battery as possible.

[Zs-ondabrain]

As I speak from experience......

Run a single larger gauge power wire toward the relays. Fuse that wire either at the battery or near the relays. Split the power wire (1-10 gauge power wire, split into 2-12ga wires.)

Ground the headlights seperately, Close to each headlight. No need to star ground these, no electrical noise issues. Just keep the grounds short and tight and clean.

Been doing this for about 25 years now. Actually make a good living at it. So do what you want but K.I.S.S. Keep it Simple Stupid.

Dave

[Mikez73]

I think I'll keep it simple Whenever I try to think about electricity everything goes gray and I start getting sleepy . I don't see any 10amp fuses in your harness. Unnecessary?

[Zs-ondabrain]

I use a single 30 amp fuse just before the split into the relays. I use 30's because there are normally 2) 10 amp fuses but a lot of people (like me) have higher output bulbs (I use 90/100 H4's)

You could probably use a 20 or 25 but 30 is good.

Dave

[pwd]

Fuses are to protect the wire, not the load. Size the wire to the nominal load current, then fuse it. In the event of a chaffed/shorted wire, the fuse blows instead of melting the wire and causing a fire.

[Zs-ondabrain]

I fuse mine near the relays because some people like to connect the power wire to the Alternator, starter or the battery. They of coarse have to Cut the wire to size when doing anything other than the battery, and this leaves the fuse holder in place and untouched. Gotta think like everyone else might, when building products that go all over the World.

Dave

[Mikez73]

I can't figure out how you do the parking light relays. That looks more complicated than the headlights.