Hello Gentleman and ladies,

Happy Thanksgiving to all. Just a quick question I'm sure one of the Gurus will know. Which color wire on the 2 prong alternator plug is switched 12v - I have no way of checking right now but trying to do some wiring.

rich

 

None of them.

The big red wire is connected right to the battery, and the two smaller wires go to the regulator.

- Eric

 

Hey Eric,

I understand that but which of the 2 wires in the plug is the switched 12v?

 

The Blue Field wire carries current to the field coils when the engine is running.
When the engine is not running and the key is On, it is (+), with current supplied through resistors, so it is not a full 12v.
When the engine is running, the relay closes, and it is fed by the regulator depending on the load.

The White Relay wire is energized by the alternator when the engine is running, and switches the Field wire from exciter current to regulator current.

So I guess you mean the Field wire.

- Eric

 

Hey Eric,

What I really mean is that I have done an engine swap - 5.3 LS with a carb - msd ignition box and was wondering since the ls alternator uses 1 wire can I use one of the wires existing in the harnes right there? Any thoughts would be appreciated.

 

Oh. You need to connect an internally regulated alternator in a car with an externally regulated alternator.

The big red wire goes to the big terminal post.

If there is a sensor wire, as there is on the 10SI (the #2 wire), it goes to the horn relay.

The other wire (the #1 wire on the 10SI) goes to the ALT light.

Either of the below diagrams would work fine for your purposes.





- Eric

 

thank you - ill let you know how it works out

 

It will work out fine. Whenever Eric gets the needed information he always gets it right. I admire the way he extracts the needed info.

 

Ha ha. Thanks, Stellar. I figure it's kind of my job to digest the information and lay it out sometimes.
As long as I can understand the question, I try to come up with the answer.

- Eric

 

Eric - the alternator is a one wire LS2 series with built in regulator - not sure the 10 and 12SI follows suit. I'm reading that it's a switched 12 volt and if it has a built in reg I should probably stay away from (not use) the old wire plug, harness that went to old school alt. Make any sense?

Rich

 

Unfortunately, Rich, I know nothing about LS-2 alternators.
I do know that some alternators from the past 15 years or so are regulated by the car's computer, though.

If I weren't at work (Damn), I'd be able to research this and give you an answer, but I'd suggest asking Stellar, since he's an actual alternator / starter expert.

- Eric

 

Eric said to ask you about the ls2 one wire alternator- lol


Rich

 

A cursory check seems to show that there were a number of LS alternators, all if which look the same, but which require different (and different numbers of) wires in order to work.

Apparently, if you have a single wire to the F (for "Field") terminal, you have to connect that to a switched 12v source (which is NOT any of the regulator wires), but if you have a single wire to the B (for "Bulb") or L (for "Lamp") terminal, which is usually Brown, then you need to connect it to a switched 12v source through the ALT lamp, which would be the brown wire to the regulator (or, alternatively, wire from a switched 12v source through a 470 ohm resistor, which duplicates the resistance of the #194 ALT lamp).

- Eric

 

First, is the "LS alternator" a CS130 or a CS144?

Whichever it is, Google the wiring diagram for that model. These alternators are set up with a four wire plug, but there is a lot of flexibility as to how you wire it. For example, there are separate terminals for the GEN light and for non-light applications. You only need one of those two, not both. Similarly, there is a wire for ECU control of output that is not required unless your car has this function. All this info is an extremely short Google search away. We should not be guessing or speculating when it's very easy to get the correct answer.

 

I'm sorry I don't have Eric's finesse. I need to know what year make model and engine the alt you are using was built for. I guess this is for 2005 or later. If this is the case, and you have a 1 wire regulator in the alt then usually the only wire in use will be the battery positive wire. In most cases that I am aware of, the lite function on these later style alts will not function if fitted with a 1 wire regulator. If it is a 2005 or later it may be an alternator manufactured by Delco Bosch or Valeo. If it has a 1 wire reg in it then a lot of research would be needed to be done because the reg would be aftermarket and the specific functions of each of these aftermarket regs are not in my realm of knowledge. If you need a switched wire to make the alt work, then it is not a 1 wire. If you do need a switched wire, try to let me know what alt you are using. A pic would help. If Joe is right and it is a CS130 or CS144 with a one wire reg the lite will not function on these I am sure and no switch wire is needed. If it is a later model alternator, do not connect a switched wire until you know what is needed as damage to the regulator may occur.

 

Huh?

Let's start again. The CS130 and CS144 alternators have a four wire plug that can be used in a multitude of ways. If you wish to retain the GEN light, simply connect the "L" wire in the plug to the brown wire that goes to the light. If you have a voltmeter and don't use a light, simply connect the "F" wire in the plug to a switched +12V source. Only one of those two wires is used in each installation, not both. The "S" wire is the sense wire and gets hooked up as normal. The "P" wire is only used for ECU-controlled applications and can be ignored. Again, this is well documented online, including available Delco literature.

 

100% correct Joe. My bad. I misread a previous post thinking he was using a 1 wire alt. Sorry about the unecessary info about the CS units having a 1wire reg. If it is a CS 1 wire the light won't function and it won't activate the alt even if it is connected, but no harm will occur. If he connects it like you said there should be no problems.