Alternator Conundrum
03-26-2016, 09:54 AM
#1
Alternator Conundrum New crate LS3 going in old Volvo. Using a new/replacement 160A alternator for a 2010 Silverado. Picture of the 2-prong plug below. I've been asking anyone who'll listen (and even a few that won't) if they know where the two terminals in the plug should be connected. Seems to be a mystery of epic proportions. Can anyone with experience shed some light? For reference purposes, we can refer to the picture of the plug from the perspective of the terminal on the top and the one on the bottom. My car had a sbf 5.0L in it for 19 years -- I have the alternator light/exciter wire marked - pretty sure it goes to one of these, but no idea which one or what the other one should be hooked to. Thanks in advance for any help.
03-26-2016, 10:50 AM
#2
With help from another swapper, I was lead to this bit of tech --- seems to be on point. Perhaps it will help others in the same boat.
http://www.trifive.com/forums/showthread.php?t=116343
http://www.trifive.com/forums/showthread.php?t=116343
03-26-2016, 12:15 PM
#3
TECH Senior Member
iTrader: (7)
With help from another swapper, I was lead to this bit of tech --- seems to be on point. Perhaps it will help others in the same boat.
http://www.trifive.com/forums/showthread.php?t=116343
http://www.trifive.com/forums/showthread.php?t=116343
Andrew
03-26-2016, 12:50 PM
#4
I'm just going to trade out the 2-pin GenIV alt for a 4-pin GenIII at the parts store. But I'll take any elaboration you can give regarding the terminals, which one is L and/or S and exactly what gets wired to what....thanks Andrew! Headed to the parts store now....
03-26-2016, 02:25 PM
#6
You mean a 160A with the 4-pin regulator? Is there any way to tell 2-pin from 4-pin with year/make/model without physically looking at the alternator? I suppose it's the switch from a GenIII to a GenIV computer? In other words - if it's 160A in a GenIII motor/ecu - then it will have the 4 pin? Which leads to the obvious question - is there a reliable listing of year/make/model and whether they have the III or IV engine/ecu?
03-27-2016, 06:24 PM
#7
9 Second Club
When my early LS1 alternator **** itself the last time, I ordered one of these.
Simple "old car" fitment same as my early LS1.
ie 1 big live wire hooks up, and 1 wire to excite the alternator via the light on the dash.
Keep it simple. I think you can specify different needs when you order anyway
https://alternatorparts.com/ad230-ad...ternators.html
Simple "old car" fitment same as my early LS1.
ie 1 big live wire hooks up, and 1 wire to excite the alternator via the light on the dash.
Keep it simple. I think you can specify different needs when you order anyway
https://alternatorparts.com/ad230-ad...ternators.html
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03-27-2016, 07:14 PM
#8
Thanks for all the help guys. I've been able to easily source a 130A 4-pin and a 145A 4-pin (Escalade) so either should work fine. Looks like the P terminal is left alone, the L terminal connects to the alternator light/exciter wire. Still some confusion over the other two terminals though. Above, Andrew mentions wiring up the "S" terminal, and in the trifive forum I linked above, the poster doesn't mention the "S" terminal, but rather suggests the "I/L" terminal gets connected to a switched 12V wire. I think this is the last piece of the puzzle - can we get any consistency on the function of the S and I/L terminals? The terminals on the alternator I have are labeled P, L, I/F and S.
Here's a piece I found on a chevytruck site:
"Here's a bit more technical electrical information for the CS style alternators.
The 4 pin plug has connections marked S, F, L and P. NOTE: If your alternator as an 'I' in place of the 'L' connection, see the paragraph below.
S = Sense
F = Failure (Indicator)
L = Lamp
P = Pulse
The 'S' connection connects to a remote voltage sense location. This wire connects to the larger gauge wire that was on the stock SI alternator connector (Not the thick battery wire that connects to the rear of the alternator). As it sounds, the alternator uses this connection to sense the remote voltage to determine if it's sagging (more current required), or not (less current required).
The 'F' connection is the failure indicator and is not used for our setup. It normally would go to a alternator failure indicator in some setups (as opposed to an alternator lamp).
The 'L' connection is the lamp connection. The 'lamp' refers to the typical idiot light for an alternator. This connection requires switched (ignition) voltage through between 35 and 350 ohms of resistance. If the alternator sees below 35 ohms of resistance, the CS alternator will fail eventually. For the 4th Gen Monte Carlo SS, the thin brown wire that normally went to the stock SI alternator is switched voltage, but the resistance is too small. I measured mine at 15 ohms to ground. Since this is less than the 35 ohm minimum requirement for the CS alternator, you need to add a resistor in series with this brown wire, to the 'L' lamp connection. I chose a 40 ohm 5 watt resistor. As long as you keep the total resistance between 35 and 350 ohms, you should be ok. If in doubt, measure the resistance of your brown wire to ground with ignition off to determine your car's baseline resistance.
The 'P' connection is not used in our application. It's a pulsed output that connects to a tachometer in some applications.
For alternators that have an 'I' connection in place of the 'L' connection, the wiring requirements are a bit different. See this link for more information." No link provided, of course....
Here's a piece I found on a chevytruck site:
"Here's a bit more technical electrical information for the CS style alternators.
The 4 pin plug has connections marked S, F, L and P. NOTE: If your alternator as an 'I' in place of the 'L' connection, see the paragraph below.
S = Sense
F = Failure (Indicator)
L = Lamp
P = Pulse
The 'S' connection connects to a remote voltage sense location. This wire connects to the larger gauge wire that was on the stock SI alternator connector (Not the thick battery wire that connects to the rear of the alternator). As it sounds, the alternator uses this connection to sense the remote voltage to determine if it's sagging (more current required), or not (less current required).
The 'F' connection is the failure indicator and is not used for our setup. It normally would go to a alternator failure indicator in some setups (as opposed to an alternator lamp).
The 'L' connection is the lamp connection. The 'lamp' refers to the typical idiot light for an alternator. This connection requires switched (ignition) voltage through between 35 and 350 ohms of resistance. If the alternator sees below 35 ohms of resistance, the CS alternator will fail eventually. For the 4th Gen Monte Carlo SS, the thin brown wire that normally went to the stock SI alternator is switched voltage, but the resistance is too small. I measured mine at 15 ohms to ground. Since this is less than the 35 ohm minimum requirement for the CS alternator, you need to add a resistor in series with this brown wire, to the 'L' lamp connection. I chose a 40 ohm 5 watt resistor. As long as you keep the total resistance between 35 and 350 ohms, you should be ok. If in doubt, measure the resistance of your brown wire to ground with ignition off to determine your car's baseline resistance.
The 'P' connection is not used in our application. It's a pulsed output that connects to a tachometer in some applications.
For alternators that have an 'I' connection in place of the 'L' connection, the wiring requirements are a bit different. See this link for more information." No link provided, of course....
Last edited by Michael Yount; 03-27-2016 at 07:22 PM.
03-28-2016, 10:26 AM
#11
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So wait...now i'm confused about my swap. I'm just now finishing up the wiring. The alternator that came with my engine/harness (out of a 1999 Sierra) has a 4 prong plug, with only one wire in it, going back to the PCM.
I've left this wire intact, disconnected the original external voltage regulator, and hooked the old red charging wire to the same place on the new alternator.
My assumption was that the PCM utilizes the one wire to excite the alternator when it needs to provide output, and that was all that was needed. Does something else need to be done? The original GM wiring from the truck only included one wire, from the alternator to the PCM. Is this essentially scenario #1 in the link above? If so, does this create an issue, ie, over or under charging the system?
I've left this wire intact, disconnected the original external voltage regulator, and hooked the old red charging wire to the same place on the new alternator.
My assumption was that the PCM utilizes the one wire to excite the alternator when it needs to provide output, and that was all that was needed. Does something else need to be done? The original GM wiring from the truck only included one wire, from the alternator to the PCM. Is this essentially scenario #1 in the link above? If so, does this create an issue, ie, over or under charging the system?
03-28-2016, 10:43 AM
#13
9 Second Club
My 2001 Camaro SS LS1 setup I first used ( engine swap ) had the 105A alternator that used a 4 pin plug, but only 1 wire used ( and the main big wire of course )
No idea where OEM connected this wire, I just connected it to the dash light on my car and it worked.
No idea where OEM connected this wire, I just connected it to the dash light on my car and it worked.
03-28-2016, 10:43 AM
#14
TECH Senior Member
iTrader: (7)
The L terminal is mandatory to turn the alternator ON. The S terminal is optional, but highly recommended for optimal alternator performance. It will sense when extra load is being placed on the system and adjust alternator output accordingly.
Andrew
Andrew
12-04-2016, 01:34 PM
#15
Just wrapping up some of my w-t-f? threads now that mine is up and running. Here's where I ended up on the alternator.
Below is a pic of my plug. I'm running a 4-terminal 145A spec'd for an Escalade. From right to left (starting with the red wire) -- the terminals are marked S, IF, L, P. The S terminal (red wire) goes to the power output stud of the alternator. This is, I believe, the "sensing" wire -- most folks run this to some remote location on the electrical system where it's connected to a + voltage. The reg senses voltage at this location and adjusts output at the alternator to try and hit the target voltage -- controlled/set by alt/reg/ecu. PSI Conversions insisted I connect it to the output stud, so I did. This results in my alt output voltage being right at 14.7-14.8V. The IF terminal (light gray wire) and the L terminal (brown wire) go to the ecu. There is no wire at all on the P terminal. I'm running an '08 Corvette ecu -- you can probably look up which ecu pins those wires go to. No one was able to conclusively explain to me WHY they go back to the ecu or how they interact with the ecu. Go figure. I do know that the L terminal is "ground" when the alt IS NOT charging. And when it starts charging, the L terminal puts out system voltage - around 14.7V in my case. PSI's instructions suggest that you run the "L" wire to one term of the alt light, and the other term goes on to the alternator -- effectively putting the alt light in series in the L wire. That does not work. What I ended up doing is connecting one side of the alt bulb to a switched 12V+ source at the fuse box. The other side of the light bulb is connected to the brown wire (L terminal) through a diode that allows current to flow from the brown wire to the bulb, and stops flow from the fuse box/bulb INTO the brown wire. So, when you switch ignition on, the bulb has 12V+ on one side and ground (brown wire grounded unless alt is charging) on the other - so the bulb lights. When the engine starts and the alt starts output - the brown wire now has 12V+ - so the bulb has 12V+ on both sides and with no ground = no alt light. If the alt stops charging, brown wire goes to ground and the alt light comes on.
In the end I did what it seems most everyone does --- kept futzing around with things until I got something that works without ever fundamentally understanding how that system functions.
Below is a pic of my plug. I'm running a 4-terminal 145A spec'd for an Escalade. From right to left (starting with the red wire) -- the terminals are marked S, IF, L, P. The S terminal (red wire) goes to the power output stud of the alternator. This is, I believe, the "sensing" wire -- most folks run this to some remote location on the electrical system where it's connected to a + voltage. The reg senses voltage at this location and adjusts output at the alternator to try and hit the target voltage -- controlled/set by alt/reg/ecu. PSI Conversions insisted I connect it to the output stud, so I did. This results in my alt output voltage being right at 14.7-14.8V. The IF terminal (light gray wire) and the L terminal (brown wire) go to the ecu. There is no wire at all on the P terminal. I'm running an '08 Corvette ecu -- you can probably look up which ecu pins those wires go to. No one was able to conclusively explain to me WHY they go back to the ecu or how they interact with the ecu. Go figure. I do know that the L terminal is "ground" when the alt IS NOT charging. And when it starts charging, the L terminal puts out system voltage - around 14.7V in my case. PSI's instructions suggest that you run the "L" wire to one term of the alt light, and the other term goes on to the alternator -- effectively putting the alt light in series in the L wire. That does not work. What I ended up doing is connecting one side of the alt bulb to a switched 12V+ source at the fuse box. The other side of the light bulb is connected to the brown wire (L terminal) through a diode that allows current to flow from the brown wire to the bulb, and stops flow from the fuse box/bulb INTO the brown wire. So, when you switch ignition on, the bulb has 12V+ on one side and ground (brown wire grounded unless alt is charging) on the other - so the bulb lights. When the engine starts and the alt starts output - the brown wire now has 12V+ - so the bulb has 12V+ on both sides and with no ground = no alt light. If the alt stops charging, brown wire goes to ground and the alt light comes on.
In the end I did what it seems most everyone does --- kept futzing around with things until I got something that works without ever fundamentally understanding how that system functions.