Looks alright. Although instead of taking the signal from the old headlight plug why don't you take the signal from the loom as close to the stalk and get rid of some wires and relays. Also you could lose two of those relays and just loop them at the plugs, and keep all the cable the same size (except the control circuit, you would get away with 1.0mm or 0.5mm. I would run the earth back to the battery personally, i rely on the body earths as little as possible.
1996 3.4V6 Surf that was suppose to stay stock
2013 6.4 litre HEMI V8 Chrysler 300
on 24v it'll be the negative on the other battery. using one relay wont affect the output at that length. I would use 6mm for them though (didn't know you could get 5mm). I'm guessing you got that drawing off the net? Would be careful on the numbering. Some relays are different.
1996 3.4V6 Surf that was suppose to stay stock
2013 6.4 litre HEMI V8 Chrysler 300
Hi, when I did mine I just ran 2 relays, but ran 2 wires from each, 1 to left and 1 to right bulbs. Could just loop it from one bulb to the other, esp. using 6mm. Remember that at 24v you're only carrying half the current of a 12v system, so your wires can be a bit thinner (but why bother, cost and hassle is just about the same, and fatter is always better). I also ran the earth direct back to the battery post - it's the one that connects to the earth of the vehicle. I used the original plug as the "control" signal - that way you don't have to modify the original wiring, and if mud or water gets into the relays you can revert back to the original system to test. And you can move the system to your next vehicle... Another option I added was to run a diode from the high beam signal wire (pin 86 on the high relay) to the low beam signal wire (86 on the low beam relay) - the stripe end goes on the low beam end, iirc. This setup means that the low beams stay on when your high beam is on - turning a 55/60w bulb into a 55/115w setup - really helps on twisty tracks / roads on high beam. you could put a switch inline with the diode so you could turn it off if it's an issue for warrants, but I never had an issue. NOTE: don't do this with the (illegal anyway) 100/150w bulbs. The resulting 250w of (admittedly really good) lighting pulls enough curent to melt the common earth wire inside the bulb if left on for more than about 15 minutes. Long enough to get miles away from any streetlighting... and you don't really notice one has gone till the other melts a few minutes later - total blackout and a bugger to figure out on teh side of the road.
Did mine today; went with just two relays, one for low and one for high. Took feed to switch relays from the headlight plug and used nice and beafy wire for the power, but, to be honest, i don't see much improvement, maybe 10%-20% if your lucky. And even then, with the 90/100 bulbs, they are still the worst lights i've had, and i've owned some old cars...
Looks like i'll have to replace the light inserts for some new (crystal) ones, maybe that'll help.
