alternator wiring

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eran tomer

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hello
my 95 suburban has the 8A3 option which is 124 alternator, but it had a smaller alternator.
so i bought an acdelco rebuilt unit.
now i'm looking at the wiring diagram- where should the alternator cable connect to? it's unclear.


my cable is going now straight to the battery.

and what's the purpose of the cable going from the + to the #19 part behind the headlamp?
 

AuroraGirl

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hello
my 95 suburban has the 8A3 option which is 124 alternator, but it had a smaller alternator.
so i bought an acdelco rebuilt unit.
now i'm looking at the wiring diagram- where should the alternator cable connect to? it's unclear.


my cable is going now straight to the battery.

and what's the purpose of the cable going from the + to the #19 part behind the headlamp?
I would venture your alternator is a CS144(d) unit? External fan by chance..?

Your truck probably had the alternator go there because 1) its a junction block for power in the truck for other stuff
2) headlights get good power, in an application where they may be large draws or long wire runs
3) Your truck was meant to have something special there
4) IDk man I just live here

Does your #19 exist?

Your battery charge cable CAN go to the battery but you should be careful to use what the factory used for relation to PCM and ECM, diodes, fusible links, etc.
For example, my alternator on my car goes from the AD237 stud to the postiive stud on the fuse block underhood, with a short run to the battery right next to it. However, the battery is lugged under the lug for the alternator, which is above the one for the junction block. The car has a lot of accessories tho. I think its because a feed from the alternator can keep power more sustainedwith the battery there to buffer excess and also able to step in when needed for the system at large. I think it has more to do with delicate sensors and small amp signals than anything too serious, but Im not an expert on that so that is just my assumption and observations.

Your truck has, by chance, an underhood fuse block at all?

can you show me the alt
 

eran tomer

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Yes it’s a cs144, and the car has the #19.
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this one is what they made for the positive wires, i guess it's not the factory setup:
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this one is for the grounds:
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the car does have an underhood fuse block.

btw- a scanner is showing a charge of about 13.5 while a multimeter on the battery show about 14, what does it mean?
 

AuroraGirl

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Yes it’s a cs144, and the car has the #19.
You must be registered for see images attach



this one is what they made for the positive wires, i guess it's not the factory setup:
You must be registered for see images attach




this one is for the grounds:
You must be registered for see images attach

the car does have an underhood fuse block.

btw- a scanner is showing a charge of about 13.5 while a multimeter on the battery show about 14, what does it mean?
the voltage at the point the PCM reads the voltage is .5 volts lower than a multimeter on the source of your voltage because of the charge wire and the battery being there.

Your alternator has a "Sense" wire on the 4 wire plug you can wire to a point of your chosing, it will maintain system voltage at THAT point to the set parameters such as 14.00(example). So in the case of the PCM, find the source the PCM uses, it would charge the battery to somewhere around 14.5 to keep the pcm wire at 14. that tells me you have voltage drop, a fair amount, and corrosion probably, in system wiring and connections.
 

eran tomer

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Your alternator has a "Sense" wire on the 4 wire plug you can wire to a point of your chosing, it will maintain system voltage at THAT point to the set parameters such as 14.00(example). So in the case of the PCM, find the source the PCM uses, it would charge the battery to somewhere around 14.5 to keep the pcm wire at 14. that tells me you have voltage drop, a fair amount, and corrosion probably, in system wiring and connections.

i lost you on that one...
i am going to replace the main cables.
 

AuroraGirl

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i lost you on that one...
i am going to replace the main cables.
not a Bad idea but it may not fix your problem

On your alternator, the plug has 4 connections

One of them has a specific function called "sense"

run a wire from that pin and place it where you want your truck to read "14.5" volts.
If your ECM, for example, reads it from a spot in the cab or the junction post etc, etc, (i dont know where it does) and you place the wire at that spot, that spot will be maintained to 14.5.

Because voltage drop lost you 14.5 to 14.0 before, you would be probably sitting at 15.0 at the battery in this hypothetical.

The main cables is probably where some of that loss in voltage is coming from.

The connections between all power points would be a big one too. Dont ever discount grounds as well they are important.

You must be registered for see images attach

To visually help here, the BIG ONE. The big terminal, here the wire is red. The left most pin on the plug which is only able to go one way. That is a sense wire. IF you want to improve the voltage in your system at the ECM, heres a tip. Run that to either your junction on the firewall or your starter positive lug
that should bypass a few of the large potential voltage drop situations and make it so your battery would read higher but your electronics would see the voltage you desire. Probably.
 

Schurkey

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hello
my 95 suburban has the 8A3 option which is 124 alternator, but it had a smaller alternator.
so i bought an acdelco rebuilt unit.
now i'm looking at the wiring diagram- where should the alternator cable connect to? it's unclear.

That's a really terrible illustration. The alternator output wire seems to go to the power distribution studs on the firewall. Right next to the smaller wire coming from the battery via the starter solenoid.

Look for a better illustration in the service manual, instead of in a parts manual.

The aftermarket power distribution buss-bar is a really terrible idea, in particular the positive unit. Drop a wrench on that and something grounded, and you've got an arc; maybe a welded wrench. Wild Guess: EVERY ONE of those power connections--positive and negative, including the cables at the battery, need to be disassembled for cleaning and inspection. Externally, they all look corroded. Whether they're corroded where it matters is why you need to disassemble and inspect.


my cable is going now straight to the battery.
That "works" but is probably not at all the best way.

and what's the purpose of the cable going from the + to the #19 part behind the headlamp?
Power distribution to an accessory your truck doesn't have? Maybe a power connection for a snow plow or some-such.
 
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Schurkey

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I would connect it via the OEM routing--which appears to be alternator to firewall distribution block stud, then the next stud over has a cable that connects to the starter solenoid, which then connects to the battery.

This way, the alternator power is being delivered physically closer to the loads it's powering, instead of directly to the battery--which then powers the loads through the double-long harness going first to the starter solenoid and then from there to the firewall distribution block.

The way it is now, you're powering the battery directly, but the other loads are getting power only via the extra-long cable from battery to starter to firewall distribution.
 

eran tomer

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I’ll try that but the wiring diagram shows it goes direct, and doesn’t show a power distribution bus at all.

Those bus bars that i have i guess were relocated to this spot because someone installed an MSD on the firewall. I recall you are against MSD, aren’t you?
 

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