Main wiring harness from scrath... a few questions

[unfrgivn]

Quick Background
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Hey guys, my car is an s13 with a redtop SR. I am very knowledgeable about 240's and engines (not some stupid kid with his first car). I have had this car for about 3 years (I swapped the engine about 2 years ago). This is a recently gutted track car, primarily for running track events up at Summit Point in WVA and occasionsal solo 2. It will see little to no street time, but I want to wire up signals, headlights, and stuff to pass inspection because I don't have a trailer 100% of the time to get the car to the track.

I know a decent amount about electronics and wiring in general, but haven't done much with car electrical systems, so this will be fun.

Questions Begin
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Instead of the stock system where you have several different stages of powered devices CONSTANT 12v, ACC, IGN, START... I plan on having a master kill switch off the battery which then gives power to a momentary switch and a relay to power the starter solenoid, as well as power to a main fuse block which runs all the circuits for headlamps, brake lights, wipers, signals, ecu, gauges, etc...

1. Charging System: If I ground the alternator to the engine and run the other large bolt to +12v on the battery through a 100A fuse is that good enough, to charge the battery? Do I need to worry about the 2-wire plug if everything is just runing off the battery? I don't care about the charging light or anything, but if I need it then I can just wire up an incandescent light at the end of the white/red wire and what do i do with the white wire that normally went to the driver's kick panel fuse box? Does the SR alternator need a signal to start charging like some GM ones I've worked on?

2. ECU Power: Since I have no main engine harness anymore and the plugs for ECU power over by the battery tray are gone, I need to re-think this. I've looked at the FSM many times, but I get very lost in the huge mass of stuff that I'm no longer using. I assume ECU-Backup power is a constant 12v for when the car is off so the ECU doesn't loose anything stored in memory, Then there are 2 large power wires which can just be on when my master kill switch is on, and the last wire is the orange (ignition start wire) that plugs into the ecu along with the speedo/tach/consult plug that goes over to the driver's side. Is this wire also on when ignition is on or what? Does it normally get power from the alternator at the fuse box and can therefore just get power as well when my ignition kill switch is on?

3. Headlights: Once again I have read the FSM EL section so many times my head hurts, because some of the wiring diagrams are crazy with all the different options, high-beams, running ligths, headlights, motors, dimmer, etc... I want to run a simple switch that pops up the motors and turn the lights on, lowers the motors and kills the lights when off. I could use a DPST switch and hook up a timed-relays to each pole for sending the popup motors a 2-second singal because when constant power is applied to the motors they start to short after they fully open/close. I know stock there is a timer box that controls this, but I think using a timed relay will work just the same. There will be a 3rd relay that powers the lights off the same pole as the lights up relay. I am sorry this is so confusing, because I am very confused myself. Does what I'm saying make any sense at all or has anyone created a custom headlight wiring harness without the use of the stock timer assembly or stock headlamp relays?

I have everything laid out on paper and it's starting to make sense, but any insight into the above 3 systems would be greatly appreciated!


*NOTE* I posted this on freshalloy also, so i apologize if you read both forums and see this twice...

[the head]

for the headlights since they may not travel up and down at the same speed you may want to just use two (1 up 1 down) relays and wire it to a momentary DPDT switch which you can hold until both lights raise/lower. I have a 66 corvette that is wired like this from the factory and the system works very well and is much easier than a timed relay or limit switch configuration

For the alternator I am unsure if the alt can be hooked up in the method you are describing since it is not a self-exciting (see single wire) alternator a lot of hot rod shops sell conversion kits to make alternators self exciting but IDK how to wire one on a nissan alternator. If you could get the conversion to work than yes your alternator could be wired that way. also you dont want a fuse on the alt to batt connection.

these are just a few thoughts for ya good luck with your project!

[unfrgivn]

1. I am looking at page EL-25 in the FSM and the alternator has 4 wires...

- The black wire goes to ground
- Big white wire goes through a fusible link (75a I believe) and to the battery +
- The smaller white wire on the plug connects to the bigger white wire before the fuse box
- Finally a white/red wire runs through the SMJ, through the charge light on the dash, and gets power from the 10A ignition fuse in the driver's kick panel fuse (whenever key is in ignition on or start)

So unless the signal from IGN on through the check bulb is also switching the alternator on somehow, my wiring method should make sense. Basically I don't understand fully what the purpose of the white/red wire is other than the check lamp.

2. As for headlight I considered that, but I don't want to use a momentary switch as it is an easy way out and there has to be an easy way to do it automaticalyl with a single switch and relays...

Thanks for taking a stab at it, I always appreciate any help

[the head]

ok than the smaller white wire needs to be hooked up as well that is your exciter wire which regulates current flow to the battery through the internal voltage regulator basically it is a voltage sensing wire it sees current and adjusts alternator output (lets it know when and how much to charge the battery)

[unfrgivn]

Ok that makes perfect sense, so I just need to split the wire after fusible link and run it onto the +post of the alternator, as well as that 2-plug switch.

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Can you shed some light on my question of whether it is legit to have the charging circuit isolated from everything else? Basically the alternator to battery is one circuit and then from the battery through a master kill switch to a fuse box for all the other electronics.

Just to shed more light on my plan... the battery runs into a 100A fuse and then through a master kill switch (150A continuous marine switch), which goes into the fuse box. The fuse box then has the following circuits, headlamp left, headlamp right, headlamp retract relay, wipers/washers, fuel pump, ecu, starter solenoid, horn, signals/flashers, brake lights, gauge cluster, aftermarket gauges, assorted electronics (boost controller, etc...)

In this way everything is properly fused, protected, etc... and I can kill all power to everything with the flip of a switch. Just seems like the easiest and most logical way to do it unless I am missing something key. Thanks.

[the head]

Although my nissan is not one of them I have set up quite a few projects with that ciricut arrangement Personally I find it FAR easier to troubleshoot several small fairly simple circuts than one or two very complex ones

as for the kill switch I would recommend using a four post automotive battery cutoff from flaming river or somthing the other two posts are for the exciter wire on your alternator. This breaks signal and shuts the alt down even if it is turning (if the engine is still turning the alt will continue to charge even after the batt has been cutoff) if you are using a kill switch as a way of saving your ass in an accident you definately want to use a four post kill switch