Charging problem I can't figure out.

[Ishmael]

I've tested all kinds of stuff on this and been on google and youtube. I can't figure it out. I have an aluminum LS2 out of a C6 vette in my 68 firebird. I can't get my alternator to charge. My battery is good and the alternator is a reman. I get 11.7 off both when the engine is running. There was a blown fusible link to the voltage regulator. I have 11.7 coming off the orange wire and off the brown. If I jump from the orange directly to the blue I get nothing but a spark and it didn't get the alternator going but I don't think it would because the blue wire coming off I think goes through the factory engine harness to the alternator and is no longer used. Besides isn't the LS2 alternator (4 wire) internally regulated? If I'm right either the reman alternator has a faulty regulator or the computer isn't programmed properly to start the alternator or the external regulator is supposed to somehow to something and that blue wire is supposed to somehow get connected to the alternator. Either way I got no change in voltage after jumping the orange to the blue at the regulator. What are your thoughts?
TIA

[dhutton]

You still have the original external regulator connected? It needs to be removed and bypassed.

Don

[Ishmael]

Well that's good to know. How do I bypass?

[dhutton]

Sorry I always do a complete rewire so I don’t know the details. For a start just unplug it. Did your LS harness come with the plug for your new alternator?

Don

[Ishmael]

Sorry I always do a complete rewire so I don’t know the details. For a start just unplug it. Did your LS harness come with the plug for your new alternator?

Don

It did. So with it unplugged the car still runs - just doesn't charge. So I don't need the stock external regulator? Is there a way to test the wiring to the alternator or the regulator in it? I get 11.5v off the battery post on the alternator and the battery.

[dhutton]

Good wiring diagram here:

https://www.camaros.net/forums/attac...9&d=1464084803

[dhutton]

Did your LS harness include the alternator plug? Most auto parts stores can test the alternator for you.

You don’t need the stock external regulator with an LS internally regulated alternator.

Don

[Ishmael]

Thanks Don. And thanks for the schematic. I've seen some but that was one of the clearest. The harness included the plug. I will get the alternator tested. I suspect either there is something missing from the harness (I keep reading about a resistor or a diode or something), or the computer isn't sending the message to excite the alternator.

[blitzer454]

Thanks Don. And thanks for the schematic. I've seen some but that was one of the clearest. The harness included the plug. I will get the alternator tested. I suspect either there is something missing from the harness (I keep reading about a resistor or a diode or something), or the computer isn't sending the message to excite the alternator.

If it is a 4-wire alternator then you will need to connect the "I" terminal of the alternator to a switched 12v source via a resistor in order to excite the alternator before it starts to turn otherwise it won't charge. This may be the resistor you heard about?? The "S" terminal of the alternator should be connected to the main junction point of the car which for a 68 firebird would be the horn relay.

[dhutton]

If it is a 4-wire alternator then you will need to connect the "I" terminal of the alternator to a switched 12v source via a resistor in order to excite the alternator before it starts to turn otherwise it won't charge. This may be the resistor you heard about?? The "S" terminal of the alternator should be connected to the main junction point of the car which for a 68 firebird would be the horn relay.

That connection is normally supplied in the LS conversion harness alternator plug. At least it has been in all the ones I used.

Don

[blitzer454]

That connection is normally supplied in the LS conversion harness alternator plug. At least it has been in all the ones I used.

Don

My harness had a wire labeled GEN but it was never clear to me if that was meant to be used as the exciter wire or if that was a pwm wire to be used on the newer alternators that support that feature. Originally I was using it as the exciter wire and it was working, but in the end I decided to use a resistor to a switched supply.

[dhutton]

Make sure the engine, frame, and body are properly grounded.

[Ishmael]

Make sure the engine, frame, and body are properly grounded.

I’m pretty sure it’s all grounded.

[Ishmael]

So I took it into the parts store to get the battery and alternator tested and when the guy at the store hooked up his machine it was reading 14.1v when the fan, stereo and lights were on it was 13.8 or thereabouts. My multimeter tested the same. When I got it home it was back to 11.6v.
I would assume the alternator then isn't the culprit. The battery checks out. The computer must be good because it sent the signal to start the alternator and the harness must have whatever it needs in it. Can a horn relay cause this and can they go good and bad? Unless a diode or whatever is being used for resistance can go in and out it has to be a connection, a ground or a broken wire in the harness and since I have already had one of those, things could get interesting. I have an aluminum engine block. I have heard about issues there but I have ground straps from the engine to the body and the frame and cables off the battery to the frame and the block.
My wife won't go anywhere in the car and I don't blame her.
What am I missing?

[dhutton]

Did you put a voltmeter right on the alternator post and measure the voltage with the meter ground on the block? What does it read?

Are your fans running when you are doing this test?

Don

[dhutton]

Who made your harness?

[Ishmael]

PSI made the harness but it was years ago. I have had problems with either the harness, the connection to the trans or the tune that has stopped me from driving it forever. When I ground on the block I don't get any change.

[Ishmael]

Sorry it goes from 11.6 Just off the battery to 11.4 off the post to the block.

[dhutton]

What is the voltage right on the alternator stud?

Don

[Ishmael]

As of right now everything off the stud on the alternator is 11.42. Across the battery though it’s 11.52 if that makes a difference.