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Alternator wiring

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I'm working on Re-wiring my 78 brat.I will use an EJ alternator with the ej22 until I find a better alternator.However that is not my question.On the 78 Brat it has a yellow wire and a black/white wire at the alternator.Correct me if I am wrong but the yellow wire should be switched 12V,while the black/white wire should be 12V constant at the most electrically distant location.

 

First of all am I correct in the function of each wire or do I have them backwards?

Secondly I will be running the battery in the bed behind the cab on the right corner,So I am wondering where the most electrically distant location would be.

Should I run the black/white wire to the battery or should I find a 12V constant wire in the main harness after the fuse box?Finally of the original wires for the external regulator I have a 12V constant white wire(I would connect the yellow wire to it but it wouldn't be very far from where the output on the alternator would be), a white/red wire, and a large black/yellow wire.Which of those wires can provide the 12V switched power that the alternator needs?

 

Oh yea,I wont be running the factory instrument cluster so the switched power wont be coming from the charge light, because the instrument cluster and most of its assorted wiring wont be there.I'm running aftermarket gauges and only keeping the left/right indicators as well as the high beam light.

Edited by Uberoo

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I think you are incorrect on your wires....Basically you can ignore most of the EA wiring......since it's for External regulated.

 

White red wire at the Regulator is the Charge lamp.   If you aren't using the orignal dash......just ignore that wire and add you own charge light.

 

If you are using an 95 or newer EJ alt......that's the only wire it needs other than the Main charge wire.

 

 

 

If you are using an Older EJ alt....You also need an Ig. switched power source.

 

What year Alt are you using?  What shape and how many pins in the plug?

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Initially I will use the alternator off a 90-94 ej22 until I can find a high amp replacement.

 

I'm not running a charge light,the aftermarket gauge kit comes with a voltmeter.

Edited by Uberoo

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Initially I will use the alternator off a 90-94 ej22 until I can find a high amp replacement.

 

I'm not running a charge light,the aftermarket gauge kit comes with a voltmeter.

 

Well.....you kinduv need one......It needs a "loaded" voltage to excite the feild.....

 

Meaning a voltage not just from Ig. switch......but through a draw of some sort first, so that there is a drop in voltage on that circuit relative to the other "Sense" wire.

 

The sense wire that for that Alt is where the EJ's Yellow wire would be......switched 12v same circuit as ECU power on. 

 

Later models there is no switched power wire.....just the charge lamp and battery voltage for sense.

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Right now I am just setting up the wiring to use any 3 wire style alternator so I am dealing with the wiring in the car itself not so much for any specific alternator.If I run the alternator's sense wire to the most distant electrical part it will have a drop on it.In my case the most electrially distant location is the fuse panel.With the rear mount battery power first goes through a breaker,then onto the starter lug,The main fuseable links take power from the starter,then to the ignition switch,Then by taping into a wire that has 12V+ when ever the ignition is switched on goes to the fuse panel,then finally to the alternator itself.While the alternator's output is ran to the starter with a inline fuse.That my not be how the wiring was from the factory but with the rear mount battery its kinda needed.So while I have the 78 brat body harness on my living room floor I need to wire the alternator wiring for any possible 3 wire alternator.So on the alternator itself which wire does what?Currently the connector is a standard 2 pin connector like this --|.

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You need an ALT light.  Period.

 

If you don't put a load on that circuit.......when you turn the key to on it will blow the fuse for that cicuit (or just fry it if not fused propely)

This is because until the alt starts turning......that terminal is GROUND......go ahead......run a 12v wire straight to it and see what happens.  When the alt starts spinning the Voltage goes up and drives that line high........turning off the light.....this balance of 12v at the bulb is critical to properly excite the field.

 

 

You want the sense wire on the ECU circuit......since that is the most critical place to have stable voltage. 

 

I don't know why you think it has to be "electrically distant"    They don't hook up alternator circuits to the taillights now do they???  get that out of your mind.

 

You need an alt light.

 

Some alts use switched sense.....other straight to the battery but unless we are talking one wire GM there needs to be a charge light.

 

BTW.......run the Charge wire through a Fusible link.....or a Maxifuse......not just an inline......it needs to be able to handle the Alts max amperage.  So......at least 85 AMPs......I would think a 100 or 120 amp maxi fuse would be good.

Edited by Gloyale

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I don't need a charge light if I wire a diode in place so current will only flow from the ignition switch and not the alternator.So once again which wire will provide switched 12V to the original voltage regulator?

Edited by Uberoo

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I don't need a charge light if I wire a diode in place so current will only flow from the ignition switch and not the alternator.So once again which wire will provide switched 12V to the original voltage regulator?

 

The shorting out happens from running 12v directly to a ground source........which the "L" terminal is until the alt starts spinning.

 

Adding a diode would not help.  your are still putting 12v directly to ground........if there is no load.....it will fry the circuit.  IN fact the diode will PREVENT the Alt from being able to turn off the charge light........not excactly sire what that would do but it wouldn't be good......could make the Alt full field all the time...(until the fuse blew or wire fried)   If anything......you'd need a Resistor.....not a Diode.

 

 

Look......I've wired up EJ alts in DOZENS of vehichles now.............went through lots of headaches with Gen 1 external regulated setups.......Studied and seached and figured this all out to were I could wire your EJ Alt to any 12v system and make it work.............BUT IT WOULD NEED A CHARGE LIGHT!

 

 

I don't understand the resistance to having a charge light......It's a great way to monitor the Fielding cicuit.

 

I also don't understand the resistance to good advice........You asked.......we gave the answer.  Fry your wiring all you want or listen to the answer since you are the one that asked in the first place.

 

 

B/W wire is Switched 12v

White/red is charge light

Edited by Gloyale

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My hatch I bypassed the wiring for a charge light and even had its wiring switched 12V.It worked fine other than when I first hooked it up the wires I had them backwards and it would drain the battery.A diode works because it blocks the flow of current.With no current flowing there will no voltage on that circuit.Electricity works by having a complete circuit-a path to and FROM a load to a power source.If current isn't flowing on one leg it wont have any voltage or current on the other side of the circuit until something completes the circuit.A simple circuit with a battery a light and a switch and some wiring will show that.The light will only come on if the switch is closed.If you replace that switch with a diode-depending on how the diode is orientated, current will flow and the light will turn on or current wont flow and the light will not come on.remember the factory EJ wiring used a diode for that exact purpose. 

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My hatch I bypassed the wiring for a charge light and even had its wiring switched 12V.It worked fine other than when I first hooked it up the wires I had them backwards and it would drain the battery.A diode works because it blocks the flow of current.With no current flowing there will no voltage on that circuit.Electricity works by having a complete circuit-a path to and FROM a load to a power source.If current isn't flowing on one leg it wont have any voltage or current on the other side of the circuit until something completes the circuit.A simple circuit with a battery a light and a switch and some wiring will show that.The light will only come on if the switch is closed.If you replace that switch with a diode-depending on how the diode is orientated, current will flow and the light will turn on or current wont flow and the light will not come on.remember the factory EJ wiring used a diode for that exact purpose.

 

The diode in the factory EJ setup is on the "sense" wire.....the same circuit that powers on the ECU with IG. switch...........NOT THE LAMP CIRCUIT.  And it's there to prevent the ECU from keeping the IG. relay closed.....  Nothing to do with the field circuit.  The diode is there to isolate the ECU......nothing to do with charging except that is the circuit monitored for voltage regulator.......not exciting the feild.

 

 

The Lamp circuit is the Feild.  Run 12v to it and you will be full fielding all the time.......and cooking the circuit when KOEO.

 

A diode only blocks current one way......so if you put 12v though it to ground....it will ground.....and either short or switch on the load depending.....With a diode there what WON"T happen is that when the ALT exictes and the "L" terminal goes high volts it won't be able drive the light off......Because the diode blocks the flow in that direction.

 

That just is not the correct way to wire the system.

 

 

 

 

If you are the expert.....and know what to do then do it and don't bother asking.

 

You asked.....we answered......you are still totally confused and incorrect.

 

Hope you figure it out and don't burn up your project.  I liked wheeling with ya.

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Not only has this thread derailed enough that it hasn't answered my original question but it devolved into a flame war.Terrific.

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I am not flaming you.

 

I am trying to give you accurate information you asked for.

 

"L" terminal is for the charge lamp.....needs switched 12v THROUGH A LOAD to excite the feild.

 

"S" terminal gets either Battery volts......or switched 12v.....depending on what model used.  Doesn't really matter....this is just reference for the Voltage Regulator

 

Main Charge wire should go back to battery through a Fusible link or Maxi fuse

 

I was serious I liked wheelin with you Robert.  My intention is always to help.  Sometimes that isn't clear.....sorry.

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Just to make sure the red/white wire for the headlights is the low beam wire right?Its the only wire other than grounds that goes to both high and low beams.

Edited by Uberoo

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nevermind the red/white is the high beams.I will run the field/L wire to the same 12V switched power that the ecu will get power from and I will wire in a 50 ohm resistor,While the S terminal will be upgraded to a bigger wire and ran back to the breaker at the rear mount battery.

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"I will run the field/L wire to the same 12V switched power that the ecu will get power from and I will wire in a 50 ohm resistor"

 

This should at least work......although the resitor may cook after some time....IDK.  50 ohm may be too high also.....the little tiny lightbulb is probably only light 5~10 ohms....Prolly should measure one to find out.

 

 

Seriously.....though.......I have to ask...........Did you have a Tramatic Childhood Accident involving a Lite-Brite board???  I means Seriously......why so much resistance to a tiny light bulb??? (pardon the pun)

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Very nice,what is that alternator meant for?With 200 amps I bet you have 14.4V volts at idle even with all of the lights on as well as a ton of offroad lights. What size cable is the output to the battery?

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It's a Delco CS144 from older Chevy 350/454. At idle it puts out about 100A. There are lots of upgrade parts at alternatorparts.com

 

I have a #1/0 welding cable running to dual batteries.

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