Help please

[mikec801]

71 C20 long bed charging system issues please help. I went from driving the truck to needing a jump. I replace the battery voltage regulator and put a 12 SI Remy Delco upgrade in wiring was a mess and I pretty much got it back to where it should be. But I've blown to voltage regulators and now the 12 SI. (think it's a12 bought it used) why. The schematic shown on the threads are close to mine but a couple discrepancies one being the harness for my rear lights light green shows a loop or two coming out I only have one

[truckster]

If you're using a 12 SI (SI stands for Systems Integrated) you have changed to an internal voltage regulator and shouldn't be using the external regulator. There are a number of wiring diagrams on the board for how to make the change.

[VetteVet]

Here is how to wire the 12 SI and yes you don't use the external regulator so leave it unplugged.

[mikec801]

I followed the schematics to a T as shown in the threads I eliminated the voltage regulator completely around the brown wire and ran hot to the alternator. My concern is the black and white stripe and the black wire from the cluster connector do I still use those

[dmjlambert]

Yes, you can use those. They're not directly related to the alternator type. Those are the wires that have the in-line fuse holder near each headlight. They are for the ammeter (battery) gauge.

[VetteVet]

Those are the battery gauge wires and you have to use them to get the gauge to work. If you run the alternator charging wire to the battery positive, the gauge won't work because it reads the voltage potential between the battery and the alternator.

The solid black wire connects to the right fender terminal and runs directly to the cluster plug to terminal 1. The black wire with the stripe runs from the alternator junction directly to the cluster plug to terminal 12. There are two four amp fuses one each wired in series in each wire to protect the gauge.

There should be a charging wire running between the alternator junction and the RT. fender terminal called the SHUNT. It is what connects the battery gauge between the alternator and the battery so that the gauge can read the voltage differential between the alternator and the battery.
This all sounds complicated but it really isn't.



Here's a picture diagram showing all of it.




Here's a picture of the fuse

[NC_John]

What is the function of e brown wire? Best i could tell from the schematic it was for the battery/charging idiot light so i removed it (went through my harnesses for my ls swap this past weekend).

[Myoldtruck]

Only thing I can contribute is. I used LMC bypass plug at the old voltage regulator. Installed a late 80s camaro intermal regulated alternator. Havent had a problem since. There was a adaptor plug for the back of the alternator also if I remember right.

[VetteVet]

Originally Posted by NC_John

What is the function of e brown wire? Best i could tell from the schematic it was for the battery/charging idiot light so i removed it (went through my harnesses for my ls swap this past weekend).

The alternator needs a voltage to excite the fields (magnetize), and it also needs a resistance to protect the diode trio in the alternator. It uses keyed ignition power for this voltage, and the resistance of the light bulb (10 ohms) to protect the diodes. The light is an indicator of charging condition, because it is powered by the ignition switch, and it grounds through the alternator via the brown wire and the external regulator which the brown wire activates.

The light will come on when the alternator is not charging if the key is on, and the engine is not running. Once the alternator starts charging it puts 12 volts on the light on the alternator side and, with the 12 volts on the light from the key switch, the light will go out, because there is no path to ground for the light.

Here is a diagram to illustrate this.



If you look at the diagram you will notice a resistance wire in parallel with the brown light wire. GM installed this wire in case the bulb in the light blew out, the system would still work and be protected. If your truck doesn't have the light but has the battery gauge instead, it will have just the resistance wire which runs from the key switch to the firewall block and connects with the brown wire that goes to the external voltage regulator.

The wire labeled "orange" is actually a red wire in the truck harness and the white wire is the exciter wire to the alternator. /the blue wire is an extension of the orange (red) wire to the alternator for voltage sensing and to provide more or less current to the alternator fields to increase or decrease the charge rate which is controlled by the regulator.

When you do the conversion to the internally regulated alternator the diagram changes, and the wires go directly to the alternator thusly.



Are you sorry you asked?

Originally Posted by Myoldtruck

Only thing I can contribute is. I used LMC bypass plug at the old voltage regulator. Installed a late 80s camaro intermal regulated alternator. Havent had a problem since. There was a adaptor plug for the back of the alternator also if I remember right.

Yes the bypass plug just did the same thing we illustrated above in the early posts. It jumps the brown and blue wires and the red and white wires to the alternator, to bypass the external regulator. It doesn't matter whether you jump the brown and white or the brown and blue wires as long as the brown wire is extended to the no.1 terminal and the red wire is extended to the no. 2 terminal on the alternator.

The adapter plug at the alternator allows the square plug, externally regulated wiring, to plug into the rectangular plug for the internally regulated alternator.


Here's a picture showing how the regulator plug is jumped.





Notice the brown and white wires are jumpered and the blue and red are jumpered. Like I said it doesn't matter as long as the brown wire ends up on terminal 1 of the alternator and the red ends up on no. 2.

If they are crossed up, then the engine will not shut off with the key, and the alternator will drain the battery overnight.

[NC_John]

Originally Posted by VetteVet

.

Are you sorry you asked?

.

Absolutely not. Got some learning and found out I was right. I'm keeping my red excitation (to battery) alternator wire and letting the swap harness manage the rest.

Thanks for the time to explain and illustrate.

[dmjlambert]

I have a question please. On a gauge cluster truck, I'm thinking the brown/white wire is the resistor. Is the wire going to the light in this diagram the "fuel gauge feed" pink wire that also supplies power to the temp and brake lights and the temp gauge? If so, could I add a generator warning light by simply powering it from the same pink wire, and add a brown wire at the point the brown/white wire comes into the cab?

[VetteVet]

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

Originally Posted by dmjlambert

I have a question please. On a gauge cluster truck, I'm thinking the brown/white wire is the resistor.

Yes I thought I had mentioned that in a post above. It shares the ACC terminal on the key switch with the 12 gauge brown ACC wire.

Is the wire going to the light in this diagram the "fuel gauge feed" pink wire that also supplies power to the temp and brake lights and the temp gauge?

Yes the diagram below shows that very thing.

If so, could I add a generator warning light by simply powering it from the same pink wire, and add a brown wire at the point the brown/white wire comes into the cab?

You betcha, in fact you can add a "GEN" warning light by tieing one side of the light into any key on power source and then joining the other side to the brown wire on the inside of the cab, just like it shows in the modified pic you posted.

Cluster feed wiring.





This is a light dash and if you look at the top, you'll see the key switch wiring with the 12 gauge brown ACC wire and the 24 gauge brown/white resistance wire sharing the ACC terminal.






notice the brown wire just above the red wire from the headlight switch. This is the gen light wire that we tie into at the inside cab firewall block. It is 20 gauge.




Here we have the diagram of the brown ACC wire shown by the black arrows and the 24 gauge resistance wire. Following the path of the resistance wire, it leads to the inside of the cab firewall block, which is behind the fuse panel, where it joins the brown Gen light wire on the light dashes, lower left. This wire is not included in the gauge cluster trucks.






Looking at the fuse panel, you can see the pink cluster feed wire coming into the panel and just to the right it goes out and up to the cluster plug to the no. 3 pin on gauge dashes, and to pin 7 on light dashes.

Now if you wanted to be slick you can use the temp light socket for your GEN light. Just install a bulb and run a brown wire from pin 5 on the cluster plug down to the inside of the cab firewall block to join the resistance wire, and bingo you have a GEN light. Careful though it may be green.

[dmjlambert]

Originally Posted by VetteVet

....Here we have the diagram of the brown ACC wire shown by the black arrows and the 24 gauge resistance wire. Following the path of the resistance wire, it leads to the inside of the cab firewall block, which is behind the fuse panel, where it joins the brown Gen light wire on the light dashes, lower left. This wire is not included in the gauge cluster trucks.

Thanks. I think you may have meant to attach a different picture. The black arrows point to the main accessory feed brown wire that is included in the cluster trucks, and the brown arrow points to the brown wire that is not included in the cluster trucks and that is the wire I propose to add in order to add the gen light, and I would need to add it to the firewall entry point side of the brown/white wire. Agree?

[dmjlambert]

Now that I read your post a couple times, I think you just had a different way of saying the same thing and you did answer my question. You just didn't have an arrow pointing to it, but in the writing you are talking about the same wire I am. I appreciate your wisdom on this electric stuff, you explain things very well.

[VetteVet]

Originally Posted by dmjlambert

Now that I read your post a couple times, I think you just had a different way of saying the same thing and you did answer my question. You just didn't have an arrow pointing to it, but in the writing you are talking about the same wire I am. I appreciate your wisdom on this electric stuff, you explain things very well.

Yes that's the one. Thanks and I always try to make it as easy as I can because I know how hard this electrical stuff is for most guys.