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Hey guys I have a few questions..

I'm installing a new 12si 94 amp alternator to take the place of my old 10si 63amp alternator. I was experiencing a poor charge when my stereo was on.

I'm currently deciding on how to wire the alternator, however some articles on MAD's website have caused me to rethink my wiring so I wanted to pose the question here and hopefully get some feedback.

I understand the advantage of remote voltage sensing however in powering a car's stock electronics I don't think it would be a huge advantage to run the alternator through the stock distribution point like the articles on that website claim. I was wondering what everyone's opinion of this is.

Currently I have the alternator plumbed straight to the battery to charge it up, and the distribution block gets power from the positive battery cable off of the starter. The articles say to charge the battery from the distribution block that way the alternator can power the accessories, however I fail to see the point since the power goes that way anyway through the battery positive cable.

Also, I read that swapping from the stock ignition system (in my case a V6) over to an HEI using the stock wiring harness causes the HEI system to not be able to draw enough power. Is this true? If so, what do I do to correct it? I'm assuming wiring the HEI straight to a key-on source would correct it?

Also, where exactly do the two pins on the back of the alternator connect? I know they have to do with voltage regulation and remote voltage sensing but exactly what do they do? I have a new pigtail and need to know how to wire it with a modern internally regulated alternator.

So to recap:

1. Is it alright to wire the alternator straight to the battery, or am I leaving my car underpowered by doing so?

2. Where do the 2 pins on the back of the alt connect, exactly, on a 12si 94amp alternator?

3. Does the stock wiring harness cause a modern HEI system to not be able to receive the full amount of power it needs?

Thanks!
 

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1) Yes. Now the catch to this is that you need a heavy enough gauge wire from the alternator to the battery and from the battery to the distribution block to prevent any significant power loss.

2) Here this is from another web site.


3) Yes. The stock wiring harness uses a resistive wire (usually Pink & Black wire) from the terminal block on the fire wall to the distributor. It's purpose is to reduce/limit the power supplied coil and distributor so the ignition points do not burn up or pit rapidly. In cars equipped with an HEI you just replace this special resistive wire with a normal piece of wire to supply 12V to the coil and distributor. With the resistive wire the HEI will only get 8V or 9V and not perform well if at all.

See Big Al's write up:
http://www.stevesnovasite.com/forums/showthread.php?t=157612
 

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Discussion Starter #3
Exactly the info I needed!! Thank you!
 

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I am converting from a 3 wire 68? amp to a 1 wire 140A alternator.
1- Can someone please show me how to alter the wiring, besides the MAD diagram I keep finding? It isn't that helpful.

2- I know you just need to put a couple of loops on the existing voltage regulator, but surely there is a way to remove it completely, and maybe just loop the wires?

3- Also, since my battery and solenoid are in the trunk, I was told you can run the alternator positive from the starter positive? That doesn't sound right to me.

I just converted to a March serpentine kit, adding this hot new alternator, and ...
:bounce: returning power steering that some idiot removed previously :bounce:
 

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I am converting from a 3 wire 68? amp to a 1 wire 140A alternator.
1- Can someone please show me how to alter the wiring, besides the MAD diagram I keep finding? It isn't that helpful.

2- I know you just need to put a couple of loops on the existing voltage regulator, but surely there is a way to remove it completely, and maybe just loop the wires?

3- Also, since my battery and solenoid are in the trunk, I was told you can run the alternator positive from the starter positive? That doesn't sound right to me.

I just converted to a March serpentine kit, adding this hot new alternator, and ...
:bounce: returning power steering that some idiot removed previously :bounce:
Disconnect all the wires on the (I assume) remote voltage regulator and remove it. Loop each wire back with the terminal cut off and heat shrink the ends because some are hot with the key on and engine running. Your charge indicator light will no longer work so keep an eye on that gauge.

Connect the power (output) wire from the alternator to the horn relay (assuming you have the factory one). This is the power distribution point. One wire goes down to the starter where it connects with the positive battery cable and will re-charge your battery. The other goes to the bulkhead connector and provides power to the fuse panel and ignition switch.

Steve
 

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"loop each wire back" to what, it self?

Where does the hot lead go that goes IN to the alternator, since my solenoid is in the truck. Can it go to the hot on the starter?
 

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The charging and starting systems are independent of each other. The alternator should not affect your solenoid in the trunk. I assume since you have a Ford solenoid (relay) in the trunk your main battery cable is only hot while cranking the engine. There is bound to be an additional wire (preferably an 8 Ga.) run back there to charge the battery and a wire to activate the solenoid when you crank the engine so just leave all that alone if it works properly now.

The one wire alternator is just that. It has one (large wire on the stud) wire that outputs voltage to charge the battery and needs no other wires (circuits) to operate.

If you have a 10si (not a 10-DN) now you have 3 wires that go to it. The large wire on the stud at the back with a rubber boot over it will connect exactly as it does now. A small plug on the side has two wires. Position 1 and 2 operate as follows.

Position 1 originates at the ignition switch in the on and start positions. It runs to the charge indicator light bulb in the instrument cluster and continues to the alternator. The light bulb serves as a resistor to lower the voltage on the wire and its purpose is to “excite” the alternator to begin charging. The bulb is also a charge indicator warning light. With the engine off and the key on, there is voltage on the dash side of the bulb and a ground inside the alternator which causes the bulb to illuminate. Once the engine is started and the alternator begins to output voltage, this wire outputs a voltage. With voltage on both sides of the bulb and no ground path the bulb goes out. If the alternator fails this wire will once again have a ground internally in the alternator and the bulb will illuminate warning the driver of a charging system failure.

Position 2 is the remote voltage sensing terminal and is connected to the horn relay (I think). This allows the alternator to sense the load on the system at a distribution point and adjust the output accordingly.

With a 1 wire alternator:
Position 1 is not needed because the alternator is self energizing. Typical the engine will need to see approximately 1500 RPM before the alternator will begin to charge so when you start it you should rev the engine a few times.

Position 2 is not needed because the alternator senses load on the system at the output terminal. Once it sees 14.2 volts it regulates it there. It has no way to compensate for any load with a very long wire that may create resistance. Depending on how your main power distribution system is designed you may have 14.2 volts out at the alternator but maybe only 12.5 at your fuel pump of engine cooling fans or ignition system. While these systems will operate at 12.5 volts, they won’t work as efficiently as they could at 14.2 volts.

You can just cut the wires at positions 1 and 2, wrap the ends so they don’t short out. The system should work but you will lose the charge warning light feature and the remote voltage sensing feature.

These features are important to me so I wired mine this way.


I did switch to a CS-130 alternator and an L.E.D. warning light which required a few special changes which are shown in this schematic.


Hope this helps,

Steve
 

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Cool. It is a one wire, and everything on the diagram resembles what I have in place.
Thanks.
 
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