Internal Alternator Wiring

[VetteVet]

We'll need to go back to basics here so that you understand how the battery gauge works, then it will be much easier to wire and understand.

The battery gauge reads the voltage differential between the battery and the alternator. When the alternator voltage is higher the gauge will read "charge"
and when the battery voltage is higher the gauge will read "discharge".

In other words it tells us when the alternator is charging and when it isn't.

In order to do this, there there has to be a connection between the alternator output and the battery positive terminal which each terminal of the battery gauge can be connected. Both terminals cannot be connected to the same place or the gauge won't be able to read voltage difference between the battery and alternator.

This connection between the battery and the alternator is called the "SHUNT"
and it is shown in the diagram below along with the circled 4 amp fuses in the 1 and 12 wires.

On the stock factory trucks these two wires are run to the firewall connection block and then to the gauge inside the cab.



Here is the plug connection for the gauge dash and the wiring changes that need to be made on the plug.



Here is the comparison between the idiot light cluster connections and the gauge cluster.

light cluster




gauge cluster



Besides taking the no.2 blue wire out for the oil light to mechanical oil pressure gauge, you'll have to pull the no.5 green wire for the temperature light and the no. 6 pin will be the temperature sender wire to the temperature gauge in the cluster. You'll also have to change the temperature gauge sender in the left cylinder head, to the correct one for the temperature gauge.

.................................................................................................

The alternator will say P L I S or S F L P and the L wire is the one for the resistor. Normally you won't need the I or P terminals or the F. Only the S and
the L terminals are used. Take a look at the alternator plug or the alternator body and check the terminals. You need to be sure of what type you have.

I run my conversion harness like this.




Notice the resistor in the L wire and the fuses in the 1 and 12 wires.


You'll probably need to upgrade the alternator output wire to an 8 gauge to handle any accessories like the cooling fan or a stereo amp etc.

[VetteVet]

Here's a pretty good thread on the alternator conversion for the 144
The 130 is virtually the same.

..........
http://67-72chevytrucks.com/vboard/s...d.php?t=457448

[oldschool18]

for idiot light setup the generator lamp is a brown wire.....isn't that the brown wire coming from the voltage regulator? If that's the case why would I run a wire from the number 1 spot on the cluster plug to the alternator when I could just move the brown plug from 8 spot to the 1 spot, or just run a wire from the L wire on the alternator plug to the 1 spot on the cluster plug and eliminate the blue and white wires at the alternator from the factory plug..........I have the 8ga wire to run to the battery and the temp sending unit for gauges, but I haven't found anyone who changed idiot lights to gauges and did the alternator upgrade. I don't have a problem wiring it like gmc pauls site says but just wanted to make sure I used the L wire to run to the gauge and eliminate the factory wires and add a resistor

[oldschool18]

and this is going on a 70 c-10

[gmachinz]

I'll have to find and post one of my diagrams-it makes converting alternator styles over a snap.

[oldschool18]

converting the alternator I understand, converting the idiots to gauges I understand.......putting the two together I don't understand.

[VetteVet]

Originally Posted by oldschool18

for idiot light setup the generator lamp is a brown wire.....isn't that the brown wire coming from the voltage regulator? If that's the case why would I run a wire from the number 1 spot on the cluster plug to the alternator when I could just move the brown plug from 8 spot to the 1 spot,
The brown wire is the exciter wire for the alternator, It goes back through the firewall where it joins the brown wire to the no 8 spot on the idiot light cluster plug. It also joins with a resistor wire which goes up to the ignition switch to the ACC position on the switch. This resistor wire is calibrated to 10 ohms to match the resistance of the light bulb and it also serves as a back-up in case the idiot light bulb blows. I think I posted a diagram on page 1 showing the two together.

If you move the wire from the no .8 pin to the no. 1 pin it will make the ACC position on the key switch hot all the time, because you would have to also move the regulator end of the brown wire to the hot junction of the battery and the alternator, along with the hot feed wire from the junction to the cab and the fuse panel. The other problem with your idea is that the brown wire is 20 gauge inside the cab to the cluster plug and 16 gauge from the firewall plug to the external regulator. This means that the resistance values on the brown wire will be different from the values on the factory 18 gauge wire.This may affect the gauge reading because the 1 and 12 wires along with the SHUNT are calibrated for resistance and length.

Then you have to run the 12 wire from the battery to the cluster plug with an inline 4 amp fuse. Which you will need to do anyway.

Then you will have to disconnect the two brown wires on the cab side of the firewall plug and run a new wire from the resistance wire that connects there, with the other one that you want to run to the 1 pin, and run a new wire from there to the 1 pin. Then the resistance wire will have to be run through the firewall block over to the alternator, to the L terminal on the alternator, with an additional 75 ohm 3 watt resistor soldered inline, to become the new exciter wire for the alternator. Whew I'm running out of breath.

OR you can just run the brown wire that went to the external regulator over to the L terminal on the alternator with the 75 ohm 3 watt soldered inline.


Here is the diagram. Look at the large red wires that come into the cab. The red wire from the engine bay is connected to the alternator output wire, the red wire from the external voltage regulator and the battery shunt wire. This connection is where you need to start the 18 gauge black/white stripe wire and run it to pin 1 on the cluster plug.

When the red wire from the engine bay comes through the firewall block it carries all the current for the truck. It connects to the horn relay, the fuse panel, the light switch and to the ignition switch for key on power.



This diagram doesn't show the red wire running to the key switch or the light switch but the fourth wire down from the top is the resistance wire and if you follow it down to the lower left corner you can see where it joins the brown wire which goes to the cluster plug. This wire will not be in the trucks with gauges because it is for the charging light. You will not need it with the gauge panel. The resistance wire takes that function. If your key switch does not have the resistance wire, you can just run one from the Acc terminal and install the 75 ohm resistor inline then continue it on to the L terminal on the alternator.



or just run a wire from the L wire on the alternator plug to the 1 spot on the cluster plug and eliminate the blue and white wires at the alternator from the factory plug..........No you cannot run anything to the L terminal except for a key on hot wire with a 75 ohm resistor inline to excite the alternator. If you look at my diagram above I show how to do this and also where to wire in the 1 and 12 wires for the battery gauge. This wire will eliminate the white wire in the alternator harness. The old external red wire will run to the S terminal and eliminate the blue wire in the alternator harness. Then you can run a new 8 gauge output wire from the large terminal on the back of the alternator, to the junction shown in the diagram. I'll repost the diagram below.



Here is the red wire connections to the key switch and to the headlight switch. The arrows show the brown resistance wire to the key switch and the brown feed wire to the fuse panel for the turn signals and the heater fuse.








I have the 8ga wire to run to the battery and the temp sending unit for gauges, but I haven't found anyone who changed idiot lights to gauges and did the alternator upgrade. I don't have a problem wiring it like gmc pauls site says but just wanted to make sure I used the L wire to run to the gauge and eliminate the factory wires and add a resistor

Now if you have the idiot light key switch you will have two tan wires and two green wires connected to it. These wires go to the brake sensor on the master cylinder Prop valve (brown) and the temperature sender (green) on the engine block, and to the brake warning light and the temperature warning light, in the dash cluster. The key switch grounds these two wires during starting and turns on the two lights. You won't have the temperature light wiring connection in the cluster plug, but the brake warning wire moves to the no 2 spot. These wires are shown in the key switch diagram above.

[oldschool18]

ok lets see if I got this right..........cut brown wire from regulator move it to the L wire on alternator with a resistor in between............run new wire from 12r where you showed the old wiring from regulator and alternator coming together to no1 spot on cluster plug and the run another wire from buss bar on pass side fender to no12 in cluster plug? this will eliminate blue and white wires at alternator.........S wire jumps to large post and add 8ga wire to battery.......and I eliminate brown and blue wires at gauge cluster. I didn't know there was resistance in the brown wire for idiot light setup besides for the resistance the came from the bulb, I figured I would need to wire it up with switching alternators. I was thinking if I wired the L wire to the factory wiring at alternator and bypassed the regulator and the brown wire at the cluster wasn't hooked up it wouldn't tell the alternator to charge. But since you told me everything I understand now that the brown wire goes to other things besides just the idiot light and will excite my alternator and even though it is not hooked up to the cluster and then wire up the amp gauge like you would anyways. well I hope I got this right I have been breathing a lot of paint fumes lately, and if I am right please let me know and I really appreciate all the time you have taken to spell it out for me.

[VetteVet]

Originally Posted by oldschool18

ok lets see if I got this right..........cut brown wire from regulator move it to the L wire on alternator with a resistor in between............run new wire from 12r where you showed the old wiring from regulator and alternator coming together to no1 spot on cluster plug and the run another wire from buss bar on pass side fender to no12 in cluster plug? this will eliminate blue and white wires at alternator.........

You're pretty close up to here. In fact it's right on.


S wire jumps to large post and add 8ga wire to battery.......

This will work and the battery will charge, however, remember that I said that the battery gauge reads the voltage charge difference between the battery and the alternator by using a SHUNT wire. One gauge wire goes on the battery end with the SHUNT and the other wires to the junction that the 12R goes to, along with the other end of the SHUNT. This is where the large 8 gauge wire from the alternator has to go.

Study the diagrams I posted and you can see how it's wired. In other words no.12 wire, the battery wire (fusible link), and one end of the shunt go together on the fender stud bolt, and the no.1 wire, the 12r wire from the S terminal on the alternator, the large 8 gauge wire from the back of the alternator, and the other end of the shunt wire go together on the left side of the truck. Then the cab feed wire and the no. 12 wire go from there to the firewall block and to the points in the diagrams I posted.



Now you are wondering why can't I just loop the 12R on the S terminal over to the back of the alternator with the large 8 gauge output wire since it hooks up with the output wire at the shunt junction.

Well you could, and the alternator would charge but there's a little thing called
"Voltage drop" that occurs away from the alternator, and connecting the S wire away from the back of the alternator allows the regulator inside the alternator to read this drop so it can tell the alternator to put out more juice to compensate for this drop. It will make the system more efficient and give you more power at the electrical loads on your system.

compare it to a water pressure system with the alternator as the water pump.
If you put the pressure gauge right at the pump it's going to kick the pump on and off as soon as the gauge reads the pump pressure.
Now if you put the pressure switch at the end of a 100 foot line where the pressure drop may be as much as 20 pounds below what it is right at the pump, the pressure switch will keep the pump running until it reaches the desired cutoff pressure in the line. The same holds for an air line as well.



and I eliminate brown and blue wires at gauge cluster. YES.

I didn't know there was resistance in the brown wire for idiot light setup besides for the resistance the came from the bulb, I figured I would need to wire it up with switching alternators.

Well you wouldn't with the 10 and 12 SI alternators but with the CS alternator which you have it requires more resistance to protect the internal circuit of the alternator.


I was thinking if I wired the L wire to the factory wiring at alternator and bypassed the regulator and the brown wire at the cluster wasn't hooked up it wouldn't tell the alternator to charge.

I can see where the confusion comes in here for you, that's why I detailed the wiring circuit. When you change to a gauge cluster from the light cluster you eliminate the brown wire as you know. That means you have to pick it up somewhere else to excite the alternator. Also when you change clusters you eliminate the oil pressure light and go to a mechanical gauge so the blue wire is not needed any longer. Compare the cluster plug differences in the diagrams back in the thread and you can see the changes to make in the wiring.


But since you told me everything I understand now that the brown wire goes to other things besides just the idiot light and will excite my alternator and even though it is not hooked up to the cluster and then wire up the amp gauge like you would anyways. well I hope I got this right I have been breathing a lot of paint fumes lately, and if I am right please let me know and I really appreciate all the time you have taken to spell it out for me.

Don't forget you'll need to get the correct temperature sender for the temperature gauge and move the green wire from no. 5 to no. 6 on the cluster plug.

[oldschool18]

Thanks again vettevet.........like I said before I understood the gauge cluster rewire, I already have the cluster repined and a new temp sending unit in the block. and I understood the alternator rewire it was just that damn brown wire at the cluster that had me all confused, but thanks to your very detailed info I got it now.

[VetteVet]

Glad to be of help. Have a great day VV

[sventinker]

I did the 10SI conversion today pretty much straight forward like it shows here. I used the rectifier instead of the resistor. I cut off the plug for the regulator and added female stay con terminals so my jumpers had the male terminals. On the jumper for the brown wire I just used the rectifier so it is reversible if I got it wrong and serviceable if it fails on the road. I bought the 10/12 SI plug from the store and soldered all the connections. I also used electrical grease and added some to my headlight plugs while I was there.

I found that the regulator was what failed when I pulled the cover so the upgrade was due. Plus I have a lifetime warranty on the new alternator so that is a plus.

[VetteVet]

Just for technical clarification don't you mean you used a diode instead of a rectifier, instead of a resistor.
There is already a resistance wire in the system even with the stock external regulator.

If you go to the CS alternator later on you will need to use a larger resistor.

Good job by the way.

[sventinker]

Originally Posted by VetteVet

Just for technical clarification don't you mean you used a diode instead of a rectifier, instead of a resistor.
There is already a resistance wire in the system even with the stock external regulator.

If you go to the CS alternator later on you will need to use a larger resistor.

Good job by the way.

Yes diode sorry in post #12 it was mentioned Thank you
http://67-72chevytrucks.com/vboard/s...2&postcount=12

[vince1]

I put a spare 10si on mine today. Removed connector from regulator and jumpered outside wires brown to blue. At alternator connected blue to #1. At alternator connected old output wire to #2. Ran a new #8 wire from alternator output post to horn relay junction (right on top of the one coming from the battery). Light works great, system charges at 14.6 volts and hopefully it will last a long time.

[sventinker]

I agree my headlights work great now. I plan on changing my headlight plugs and going to those fancy hid headlights. I aged some socket grease to them for now bot 45 year old electrical components need addressing

[Ewr101]

Question- The fusible link from the battery to the junction block, is its rating base on the gauge of the wire? I'm piecing my harness back together after finding a TON of bad wire and splicing covered up by friction tape wire loom; trying to get it as close to factory as possible. Also, is there also a junction block on the drivers side of the engine bay for the alt. output and ammeter connection?

[VetteVet]

Yes the fusible link wire gauge is usually four gauges smaller than the wire it protects. In the 67 / 72 trucks it is a 16 gauge protecting a 12 gauge wire and it is rated at 30 amps.





Yes the junction is nothing more than four red wires soldered together in the harness near the left headlight. If you have a gauge dash then there will be an 18 gauge black wire with a white stripe soldered there also.

Here is a picture of mine, without the B/W wire as I have a charging light dash.




Refer to the diagrams in my posts above and you will see this junction and the wires that go to it, and where they originate. VV

[Ewr101]

Thanks VetteVet. I saw fusible links at the auto parts store but was unsure of which one to buy.

I found so many splices and bad crimp connectors that were taped up, all just to get the ammeter working. The harness going across the cowl was butchered and the wire that goes to the junction by the battery for the ammeter wasn't even connected. Hell, the fuse holder was even cut out! Which leads to another question: What could make the 4 amp fuse by the driver headlight blow? (Aside from a frayed wire)

As soon as money permits, I'm going to get all new harnesses for under the hood. What I'm doing now is just to make it work, work safely and get me by till then.

[Ewr101]

Hmm.... I took my iPad to the garage with me and wired my harness just like the wire diagrams in this thread (minus the internally regulated alt.) I re-routed the battery ammeter wire to go down the left fender and across the blazer to the junction block on top of the radiator with the rest of the wiring. Engine running or not, accessories on or off, the ammeter points straight up no matter what. Any ideas? I took out the remaining glass fuse holder and put in two modern mini fuse holders since one was gone already and I still use an external regulator but other than that, it's all the same. Any ideas? Also where's the most logical place to wire a voltmeter to on the inside of the cab? PO just had wires draped across the engine bay and it looked trashy...

[LostMy65]

Originally Posted by VetteVet

....clip
[/COLOR][/B]
Study the two diagrams below and you will see that they are the same as far as the wiring . The confusion may come from the colors and numbering.
The end result is that the brown wire on the voltage regulator must go to the no.1 terminal on the new internally regulated alternator and the red power wire on the regulator must go to the no.2 terminal on the internally regulated alternator. It would appear that the diagram posted by LostMy65
has labeled the colors wrong but the wires go to the right place. I have seen that diagram before and I think it was for a Buick car which might explain the wire color difference.

Below is my MyLost65' diagram.

Attachment 1060806

here is my jumpered diagram from an above post.

Attachment 1060805

and here is the clean way to do it and if you compare all three then you can see that the end result is the same in each one.

Attachment 1060807

Below is how I did mine on my 66.
But on my 65 the brown wire is gone.
So where does the brown wire go? Or, if the colors are wrong in this particular image, What should I connect the alternator post #1 to?

[LostMy65]

Originally Posted by LostMy65

Below is how I did mine on my 66.
But on my 65 the brown wire is gone.
So where does the brown wire go? Or, if the colors are wrong in this particular image, What should I connect the alternator post #1 to?

I think I figured part of it out using this thread:http://67-72chevytrucks.com/vboard/s...d.php?t=668938
So, the brown wire would normally go to the generator warning lite bulb.
If the truck has guages, the brown wire turns into a brown wire with a white stripe that goes to what looks like the ignition switch.
Going to keep reading for where I should hook up the brown wire with the 10 ohm resistor.

[VetteVet]

This is not a hard question to answer. The brown wire that is shown in your diagram above on terminal 4 is the same brown wire that goes to the no. 1 terminal on the SI alternator. You are eliminating the blue and white wires from the OEM external regulator.

The red wire on terminal 3 is a full time battery sourced wire that should go to the no. 2 terminal on the alternator to serve as the voltage sensing wire. I talked about that in a previous post.

Back to the brown wire, This wire goes to the firewall block on the engine side. on the opposite side of the block it connects to the 10 ohm resistance wire that goes on up to the key switch. There it joins with a 12 gauge brown wire on the accesssory terminal. Look at post 2 on the upper left of the first diagram and you can see the third and fourth wires down. no. 3 is the 12 gauge brown wire that feeds the accessories in the fuse panel and the 24 gauge wire, the fourth wire down is the resistance wire that connects with the brown wire in the firewall block. It should be in the harness regardless of whether the dash is gauge or light function. If you are missing this brown wire on the engine side you will have to replace it and run the new wire to the no. 1 on the alternator.

[LostMy65]

Thanks again.
It was easy the first time when I did it on my 66 because all the wires were still intact.
My 65 didn't have the brown wire connected to the external regulator. In fact, I couldn't even find the brown wire, so I could connect to it. That's why I was asking where the brown went once it got inside the cab. I'll look under my dash this weekend to see if the brown wire and the brown wire with the white strip is there.
I did find this post by you in another thread:
http://67-72chevytrucks.com/vboard/s...79#post7948779
It makes visualizing it easier.

[LostMy65]

Okay, so I feel better.
The brown wire was still there on the inside cab side.
I dug around in my junk and found a brown wire to replace the one that was missing on the outside.
You can see from the external regulator I removed, I haven't had the brown wire for some time. Thanks again for your help VettVet