What does the "charge indicator control" wire do? (connects to alternator)
08-17-2010, 10:07 PM
#1
What does the "charge indicator control" wire do? (connects to alternator) PCM controlled alternator:
I have a 2006 truck PCM and wiring harness, and it has a wire that goes to the alternator called the "charge indicator control." This is the infamous brown wire that everyone talks about in the other alternator threads. It somehow controls the alternator...
Dash light or resistor controlled alternator:
Some early LS1 vehicles (like the Camaro) did not have this brown wire running from the alternator to the PCM. Instead, the wire from the alternator was rigged through a dash light to a B+. According to good sources on past threads, a 470 ohm resistor can be substituted for the dash light.
Is one setup better than the other? (PCM hookup vs. dash light/470 ohm resistor)
Does the PCM actively manage the alternator through this brown wire, or does the PCM just have a 470 ohm resistor in it?
Just for some background info, I have the 2006 PCM and harness, and a 1999 Camaro alternator. I do not know whether to connect the alternator wire to the PCM or to run it through a resistor/dash light. I would like to have a dash light, but I also want optimum performance from my alternator.
I have a 2006 truck PCM and wiring harness, and it has a wire that goes to the alternator called the "charge indicator control." This is the infamous brown wire that everyone talks about in the other alternator threads. It somehow controls the alternator...
Dash light or resistor controlled alternator:
Some early LS1 vehicles (like the Camaro) did not have this brown wire running from the alternator to the PCM. Instead, the wire from the alternator was rigged through a dash light to a B+. According to good sources on past threads, a 470 ohm resistor can be substituted for the dash light.
Is one setup better than the other? (PCM hookup vs. dash light/470 ohm resistor)
Does the PCM actively manage the alternator through this brown wire, or does the PCM just have a 470 ohm resistor in it?
Just for some background info, I have the 2006 PCM and harness, and a 1999 Camaro alternator. I do not know whether to connect the alternator wire to the PCM or to run it through a resistor/dash light. I would like to have a dash light, but I also want optimum performance from my alternator.
Last edited by FastKat; 08-18-2010 at 05:54 PM.
08-18-2010, 05:03 PM
#2
Any ideas?
I still haven't figured this out. With the 2007 and older trucks, it looks like two wires run between the PCM and the alternator, one is the "field" connection and the other is the above mentioned "charge indicator control" wire. Does the field wire give the PCM information, and then the PCM adjusts the alternator output by changing the resistance along the charge indicator control wire? If that's the case, what will the truck PCM do if you don't hookup the field wire?
Contrast all that with the early LS1 Camaro alternator... it has one wire that went to the dash light. All of the field control stuff is integrated into the alternator unit itself, so it doesn't need a separate field control connection.
I still haven't figured this out. With the 2007 and older trucks, it looks like two wires run between the PCM and the alternator, one is the "field" connection and the other is the above mentioned "charge indicator control" wire. Does the field wire give the PCM information, and then the PCM adjusts the alternator output by changing the resistance along the charge indicator control wire? If that's the case, what will the truck PCM do if you don't hookup the field wire?
Contrast all that with the early LS1 Camaro alternator... it has one wire that went to the dash light. All of the field control stuff is integrated into the alternator unit itself, so it doesn't need a separate field control connection.
08-18-2010, 05:15 PM
#3
It's the idiot light. Tells you if the alternator is charging or not. The resistor just takes the place of the light bulb in the idiot light. It causes a slight voltage drop that some (not all) alternators need. If you have an idiot light, best to use that. if not use a resistor.
Byt he way, "PCM controlled" alternator is a misnomer. Alternators still function exactly like they did before computers.
The field wire powers the alternator field circuit. Turn it off and the alternator stops generating juice just like it always did.
There is usually a sensor wire on alternators too. That is the voltage sensing wire. Where ever you hook that up, that is where the voltage regulator inside the alt trys to keep the voltage constant. One wire alternators just hook it up to the alternator output. That is why they don't regulate voltage as well as 3 wire alts with the voltage reference in the dash.
The only weirdness I have seen with alternators and PCM's is a phase sensing wire. Alternators generate 3 phase alternating current that gets converted to DC through the alternator diodes. The PCM on some cars (vettes) want to synchronize to the AC phase of the alternator because the slight ripple it causes in the DC voltage can confuse sensitive electronics.
Byt he way, "PCM controlled" alternator is a misnomer. Alternators still function exactly like they did before computers.
The field wire powers the alternator field circuit. Turn it off and the alternator stops generating juice just like it always did.
There is usually a sensor wire on alternators too. That is the voltage sensing wire. Where ever you hook that up, that is where the voltage regulator inside the alt trys to keep the voltage constant. One wire alternators just hook it up to the alternator output. That is why they don't regulate voltage as well as 3 wire alts with the voltage reference in the dash.
The only weirdness I have seen with alternators and PCM's is a phase sensing wire. Alternators generate 3 phase alternating current that gets converted to DC through the alternator diodes. The PCM on some cars (vettes) want to synchronize to the AC phase of the alternator because the slight ripple it causes in the DC voltage can confuse sensitive electronics.
08-18-2010, 05:53 PM
#4
Thanks for the info!
If the PCM only receives information through the brown wire, it sounds like there is no harm in bypassing the PCM. However, I don't think the truck alternator has the internally controlled field. The truck schematic shows a field wire between the alternator and the PCM. The brown wire might be significant if I was using the stock truck alternator.
If the PCM only receives information through the brown wire, it sounds like there is no harm in bypassing the PCM. However, I don't think the truck alternator has the internally controlled field. The truck schematic shows a field wire between the alternator and the PCM. The brown wire might be significant if I was using the stock truck alternator.
It's the idiot light. Tells you if the alternator is charging or not. The resistor just takes the place of the light bulb in the idiot light. It causes a slight voltage drop that some (not all) alternators need. If you have an idiot light, best to use that. if not use a resistor.
Byt he way, "PCM controlled" alternator is a misnomer. Alternators still function exactly like they did before computers.
The field wire powers the alternator field circuit. Turn it off and the alternator stops generating juice just like it always did.
Byt he way, "PCM controlled" alternator is a misnomer. Alternators still function exactly like they did before computers.
The field wire powers the alternator field circuit. Turn it off and the alternator stops generating juice just like it always did.
12-30-2013, 04:18 PM
#5
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will just using the brown wire (from a truck PCM) on a Camaro alternator Eliminating the need for a resister or idiot light connection?
Info is all over the place on this, just looking for a clear answer - Thanks in advance
Info is all over the place on this, just looking for a clear answer - Thanks in advance
12-30-2013, 04:26 PM
#6
You either need a idiot light or a resistor in series with the alternator "L" terminal. Connect the other end to switched ignition.
I highly discourage the use of a resistor because if it ever burns up you can either fry the alternator or kill the battery from lack of charging.
I highly discourage the use of a resistor because if it ever burns up you can either fry the alternator or kill the battery from lack of charging.
12-30-2013, 04:34 PM
#7
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so just connecting the L terminal to the brown wire on my PCM isn't a viable option?
I suppose I could do the light or resistor trick, I just assumed that this would work as well too...maybe I was misinformed about that or something.
The brown wire is already installed, I didn't want to do any additional wiring if I didn't need to
I suppose I could do the light or resistor trick, I just assumed that this would work as well too...maybe I was misinformed about that or something.
The brown wire is already installed, I didn't want to do any additional wiring if I didn't need to
