Ls alt wiring

[mattcrp1]

Pulling out the old thread shovel and digging this one up. My 76, with a 2002 4.8l swap, shows the brown wire 16brn25 going from the alt to the bulk head connector then to the instrument cluster but it also splits to the headlamp switch. I have a volt meter in my dash. It appears that I can just hook the original brown wire to B+?
I don't want to mess with the factory 2002 wiring by tapping into the brown wiring off of the alternator. Anyone have a suggestion?

thanks.

[mattcrp1]

So I fired it up from the key for the first time and my voltmeter on the dash was reading about 13.5v. I did not hook up the brown wire from the original alternator to anything. Any thoughts as to what I should do with this wire? Thanks

[desertdogg]

Originally Posted by mattcrp1

So I fired it up from the key for the first time and my voltmeter on the dash was reading about 13.5v. I did not hook up the brown wire from the original alternator to anything. Any thoughts as to what I should do with this wire? Thanks

I was actually missing my connector for the alternator. mine is a two pin there is a brown wire that comes out and should go to your green pcm connector pin 15, as per my engine wiring guy. Not sure if this helps or not.

[mattcrp1]

I have the blue and red pcm connectors and I am still a little lost on this brown wire and what to do with it.

[Pzary3233]

What alternator are you using? Camaro, Vette, or Truck?

[mattcrp1]

Sorry, I have a 2002 4.8l in my 1976 SWB. The 2002 appears to be "self contained" as far as what I need to do with integrating the 1976 and 2002 harnesses. I also have a question as to the blue oil pressure switch wire from the '76 harness as well.

[ls1nova71]

Originally Posted by mattcrp1

Sorry, I have a 2002 4.8l in my 1976 SWB. The 2002 appears to be "self contained" as far as what I need to do with integrating the 1976 and 2002 harnesses. I also have a question as to the blue oil pressure switch wire from the '76 harness as well.

You can just eliminate any of the original '76 alternator wiring, it is self contained on the 2002 like you said.

As for the blue wire for the '76 oil pressure gauge, you need to mount the '76 oil pressure sender in either the oil pressure sender spot of the 5.3, or you can drill and tap the block off above the oil filter, then just hook the blue wire to it and you're done.

[Pzary3233]

Originally Posted by mattcrp1

Sorry, I have a 2002 4.8l in my 1976 SWB. The 2002 appears to be "self contained" as far as what I need to do with integrating the 1976 and 2002 harnesses. I also have a question as to the blue oil pressure switch wire from the '76 harness as well.

You will not use any of the wiring from the original 76 truck except for the GEN light which will be needed to put a slight resistance on the wire.

Assuming that you have a truck alternator this is what you need to do - Copied from what I posted on the first page:

One wire goes straight to 12 volt (Pin C), the other MUST have resistance, ie gen light or resistor (Pin B)..





However as LS1Nova pointed out you can easily just leave the two wires connected to the PCM and let the PCM worry about the Alternator

Originally Posted by ls1nova71

You can just eliminate any of the original '76 alternator wiring, it is self contained on the 2002 like you said.

As for the blue wire for the '76 oil pressure gauge, you need to mount the '76 oil pressure sender in either the oil pressure sender spot of the 5.3, or you can drill and tap the block off above the oil filter, then just hook the blue wire to it and you're done.

This is correct, you need to use your original sending unit, or another sending unit that fits in the LSx with the same output as the original 76 sending unit.

[mattcrp1]

On my oil pressure issue, I also have a mechanical connection. I never had an engine in this truck so I am unsure how it was originally hooked up. Was there originally two hook ups on a "T"?

[Pzary3233]

Matt make another thread for your oil pressure issue so we don't bog down an alternator thread for it.

Oil pressure could have either been a mechanical or electrical connection depending on the vehicle's gauge. Go with what you have and you will be fine.

[ls1nova71]

Originally Posted by Pzary3233

One wire goes straight to 12 volt (Pin C), the other MUST have resistance, ie gen light or resistor (Pin B)..

This is correct if you are NOT running it through the PCM (with a carb, for example), but, if you are going EFI, just let the PCM control if and nothing has to be done with it. Even if your truck has a GEN light, which I just assumed it had a voltmeter (we all know about ass-uming ), I wouldn't use it.

As for a mechanical oil pressure gauge, check my build threads, at least one of them shows how to easily fix that with a drill and a tap. Super simple.

[mattcrp1]

Thanks guys, I really appreciate the advise. I am so close to ripping it around the block I can taste it.

[67chevy1series]

I know this must be getting very annoying to have to keep answering slightly different questions of the same topic... However while reading this thread it never was explained very clearly how to connect a (ex: ) 2004 silverado 145amp alternator to c10 wiring harness with a carbureted LS engine instead of FI. I know the red power wire which connected to back lug of the original delco alternator is connected the same, and I know there's one more wire that needs to be connected to the stock c10 alt. Harness, and I do know that when going carburated you need a resistor inline to that said wire, but which terminal on the Delphi plug and which color wire from the c10 harness go together? I bough Holley's LS swap alt. Pigtail which has the resistor already and it's positioned for the "L" terminal on my alternator, is that correct?

[elf w/capital T]

You all are just so smart. Thank you, I and many others to come appreciate it!!

[SoMsippi_B-tie]

Originally Posted by 67chevy1series

I know this must be getting very annoying to have to keep answering slightly different questions of the same topic... However while reading this thread it never was explained very clearly how to connect a (ex: ) 2004 silverado 145amp alternator to c10 wiring harness with a carbureted LS engine instead of FI. I know the red power wire which connected to back lug of the original delco alternator is connected the same, and I know there's one more wire that needs to be connected to the stock c10 alt. Harness, and I do know that when going carburated you need a resistor inline to that said wire, but which terminal on the Delphi plug and which color wire from the c10 harness go together? I bough Holley's LS swap alt. Pigtail which has the resistor already and it's positioned for the "L" terminal on my alternator, is that correct?

I have a 69 that had original harness in it and swapped to 5.3 with carburetor. I spent a few hours reading and studying about how the older style OEM wiring harnesses and the chevy alternators actually work on the older cars/trucks on this site http://www.madelectrical.com/electri...evymain1.shtml

What concerned me was that I just spent all this money to upgrade my truck, but would also be running 2 electric fans, and 1 electric fuel pump off of my battery and possibly have too high of an amperage draw and too high of an amperage output alternator and an undersized wiring harness that was almost 50 years old. Rather than taking the chance of being stranded or burning my truck down I switched to a painless wiring harness and that kit comes with the stuff you need to properly wire a 105 amp (max allowed) type CS130D alternator and make your electrical system operate off of the power output of the alternator and properly sense the voltage draw of your electrical system and charge the battery as needed. I also had to buy the plug, #30705, from Painless for the alternator so that it could be properly wired. It took several phone calls to Painless to get the right person that understood all of this and knew what I was asking, as well as what they were talking about. Also, their wire harness instructions were being revised, and at the time I downloaded this particular wire harness instruction manual from their site it had not been updated and it did not explain anything related to the newer style CS130D alternators, but the one I received in the box with the harness was the correct set of instructions and described all of this to the letter...... I also tried to talk to Holley technical because they sell a LS alternator and plug, but I could never get the right person that actually understood me or their product on the phone to help me understand how to wire it up to an existing harness, therefore I chose to go thru the effort of swapping the harness out and do not regret it.

It's worth your time to read up the explanation of how a proper charging system works on www.madelectrical.com

[Shane65]

Originally Posted by 67chevy1series

I know this must be getting very annoying to have to keep answering slightly different questions of the same topic... However while reading this thread it never was explained very clearly how to connect a (ex: ) 2004 silverado 145amp alternator to c10 wiring harness with a carbureted LS engine instead of FI. I know the red power wire which connected to back lug of the original delco alternator is connected the same, and I know there's one more wire that needs to be connected to the stock c10 alt. Harness, and I do know that when going carburated you need a resistor inline to that said wire, but which terminal on the Delphi plug and which color wire from the c10 harness go together? I bough Holley's LS swap alt. Pigtail which has the resistor already and it's positioned for the "L" terminal on my alternator, is that correct?

I am still looking for an answer to this. I'm in the same boat with my 72 GMC carb'd 5.3 and am using the stock wiring but upsized the red wire. Unplugged the connection at the regulator. Any modification to the connection needed? I have an 8 gauge wire to the battery connection of the alternator. I'm left with two wires that I'm unsure what to do with. I believe one wire is needed with a resistor and the other wire is not needed. Which wire do I use and what terminal on the truck alternator(4 pin) gets the wire with the resistor. This is almost the last step before getting the truck on the road.

[Pzary3233]

I answered your question just a few posts up:

DO NOT USE THE C10 WIRING it is too old and small to handle the amperage! Sounds like you have a handle on that part. You may use the idiot light wire (because you do need an idiot light to make this alternator charge). Simply find the wire that is connected to your idiot light in the dash and follow this post and you'll be charging in no time!

Originally Posted by Pzary3233

You will not use any of the wiring from the original C10 truck except for the GEN light which will be needed to put a slight resistance on the wire.

Assuming that you have a truck alternator this is what you need to do - Copied from what I posted on the first page:

One wire goes straight to 12 volt (Pin C), the other MUST have resistance, ie gen light or resistor (Pin B)..

[SoMsippi_B-tie]

Originally Posted by Shane65

I am still looking for an answer to this. I'm in the same boat with my 72 GMC carb'd 5.3 and am using the stock wiring but upsized the red wire. Unplugged the connection at the regulator. Any modification to the connection needed? I have an 8 gauge wire to the battery connection of the alternator. I'm left with two wires that I'm unsure what to do with. I believe one wire is needed with a resistor and the other wire is not needed. Which wire do I use and what terminal on the truck alternator(4 pin) gets the wire with the resistor. This is almost the last step before getting the truck on the road.

http://www.painlessperformance.com/Manuals/30705.pdf

[Shane65]

Thanks guys. Checked the wires for 12 volts running. Wired it up with the resistor as shown and she's charging. One more thing to cross off the list.

[72blu]

sorry for reviving this thread but Im stumped..

I just finished putting a 2002 lq9 in my 72 c10 and I'm having and issue with the ammeter gauge. It worked fine with the old 250 6 banger but ever since I put the new motor in the gauge is always reading towards the charge side of the gauge and once the electric fans come on it pins all the way to charge side. The instruction manual that came with my harness (painless performance) said to add a 5 watt resistor to the brown wire and so thats the only modifications that I've done to the alternator wiring. Im afraid that I am going to hurt the gauge by always having it pinned out... Any ideas on why the gauge is always reading towards the charge side?

Thanks ahead of time...

[Hart_Rod]

Originally Posted by clinebarger

So is 100%
"When there is loss of class 2 communication with the powertrain control module (PCM), the module will send 100% duty cycle, 13.8 volts"
"Between 0-5 percent and 100 percent are for diagnostic purposes"
"the generator battery control module is limited between 36-90%"

Bringing up an old thread. I'm wondering if the reason I can't get my GBCM to work is because I haven't connected the orange/black wire (serial data K Pin) from the GBCM connector to PCM serial data line? Any help/suggestions would be appreciated.

[Hart_Rod]

2006 Schematics: http://www.lt1swap.com/pictures/03to07schematics/2006/

[Hart_Rod]

2 wires to the alternator, 2 wires to the battery, 2 wires to ground, 1 wire to serial data port - BOOM!!, it works!!!! Thanks Clinebarger!!!!

[Daaaanz67]

Originally Posted by Hart_Rod

2 wires to the alternator, 2 wires to the battery, 2 wires to ground, 1 wire to serial data port - BOOM!!, it works!!!! Thanks Clinebarger!!!!

Reviving this thread. Can Hart Rod or Clinebarger elaborate on this? Did I miss something on this tread that you both figured out. Can you post a diagram?