Re: Stock alternator to 12 SI alternator
 

Few months old thread, but exactly what I'm going to do shortly. Should the 12R wire be upgraded to a bigger gauge. I assume 12R stands for 12 gauge, Red. Is there anything special about the wiring to make the amp meter work? Per info I found it looks like 12 gauge will flow 41 amps. Enough for a stock 37 amp alternator.

Re: Stock alternator to 12 SI alternator
 

Here'e a page that explains how to wire the amp gauge (and volt gauge).

http://6066gmcguy.com/ammeter.html

As for the 12 gauge wire, I think that should be fine, but I'm no expert. I used 10 gauge, I wanted to err on the side of caution in case I add electric fans.

Re: Stock alternator to 12 SI alternator
 

It depends on what you mean by "the amp gauge". That site does not show how to wire the stock amp gauge from a 67-72 Chevy/GMC truck. It covers how to wire an amp gauge that has a built-in shunt, so that would be an aftermarket or some other model year or make amp gauge. The stock amp gauge for 67-72 uses an external shunt. The shunt is the 12 gauge red wire that runs between the battery and alternator, and in order for that to show all charging and discharging of the battery, no accessories are connected at the battery or starter.

Re: Stock alternator to 12 SI alternator
 

Oops, thanks for clarifying that. I found that site a while ago and bookmarked it for when I wanted to tackle getting my gauges straightened out.

Re: Stock alternator to 12 SI alternator
 

I'm looking at a 100 amp alternator. If I read the charts I've found correctly, I should probably have a 6-8 gauge wire off of the alternator

Re: Stock alternator to 12 SI alternator
 

The question is, where does that wire run to? If you have a load that will be drawing a bunch of current, you can run it to that load. If you expect the battery to supply a bunch of current to a device when the alternator is not running, then I suppose the wire from the battery to the alternator and that device also needs to be fat.

I don't have any big loads to worry about although I have a big modern alternator, so I didn't do anything to the stock wiring. I suppose it will be a good idea for me to add a fusible link at the alternator to reduce the risk of the alternator cooking my 12 gauge wiring if I have a short.

If I were to add something that hogs a lot of electric current, I think I would power it from the alternator with a fat wire and use a relay to only connect that device when the alternator was running. The CS144 alternator I have supposedly has a tach output that I would send to a driver/computer for a relay. I can't think of any big current draw that I want to add. Electric fan doesn't make much sense since the engine is right there and works with a mechanical fan far better than converting rotational power from the engine to electricity and then converting that electricity back into rotating a fan. That would be very inefficient to do that energy conversion twice. Electric fans are for front wheel drive cars when the engine sits in the engine compartment sideways. Just my rambling opinion.

Re: Stock alternator to 12 SI alternator
 

This seems like as good a thread as any to post this question...
I'm sorry I can be so long-winded. The more details the better.

I've eliminated a voltage regulator before on a '69 Camaro. I did it when I did an LS swap and used the 2006 engines alternator. I did it like picture #2 in the original post with an adaptor jumper plug. Worked fine. I didn't have a roundy-round ammeter or volt meter because I had a Dakota Digital cluster...and didn't change anything in the dash wiring.

The previous owner of my truck swapped in the current '79 Nova 305.
These pics show how he wired my alternator, which has zero numbers or marking on it at all. Reman cheapy of unknown type.
It works fine. They put a Voltage gauge in which functions fine.

Now, the voltage regulator is STILL connected.
The original AC Gen. wiring is coiled up and Zip-tied intact and out of the way. The truck was obviously a 6cyl. with points and coil from the factory.

They have a 10ga wire straight from the battery+ to the BATT lug on the alternator. You can see that it's jumpered over to what I believe is pin #2 with a smaller gauge red wire.
Pin #1 has a random white 12ga wire connected with a large diode to prevent backfeed. I haven't looked at the diodes specs yet. I'm assuming the cheapy alternator he put in doesn't have that circuit so he spliced that diode inline.
That wire is run around to the HEI where it's spliced into the ignition wire. That wire is plugged into one of the Unfused spades in the fuse panel.

That seems OK for making the circuits and alternator work for a 1-wire system...but it's done in a weird way.

I'm gonna guess that alternator is at least a +/-60 Amp unit.
My question is how is all this working with the voltage regulator still hooked up? And what trouble am I looking at leaving it this way? Previous owner drove it like this for 2 years. To top it off, there's 2 Viair compressors powered by a solenoid in back for the air bags. It's powered straight from the battery.

Since all my original wiring is still in place, I guess I should rewire the charging system, but if it's working I'm wondering if I should leave it.
Oh, and I ALWAYS have a fire extinguisher in my cars.

Re: Stock alternator to 12 SI alternator
 

One thing you're missing from your current arrangement is a functional dash warning light for your alternator. For that to work, you would need to connect the brown wire from your original harness to the alternator, as described at the beginning of this thread.

My suggestion would be to eliminate your external regulator and its original 4-pin connector, and extend the wires from the original harness over to your passenger-side-mounted alternator. Also, a factory-style alternator connector is available at your local auto parts store. The terminals from your original alternator connector can be popped into this connector housing as well, if you want to reuse your original blue and white wires.

https://www.oreillyauto.com/detail/c...tor/cti0/85841

Re: Stock alternator to 12 SI alternator
 

Thanks
What I didn't include was that the GENERATOR idiot light functions fine also. Other than the fact that it stays on real dim while it's running, it comes on bright when it's supposed to...with the key to Ignition.

The other thing I noticed is a 15A fuse taped into a spliced wire on the back of the Volts gauge, which is spliced into the 12Ga pink Ignition switch wire. That's another new one on me...never heard of that before.

I've got connectors and everything I need...just trying to make heads or tails of HOW this damn thing works and isn't on fire. 😁

Re: Stock alternator to 12 SI alternator
 

Some people are interested in getting something wired up not necessary correctly, but getting it to the point where it mostly works and doesn't seem to catch on fire, and they are satisfied. It's a matter of attention to detail. With the original alternator wires zip tied and out of the way, the regulator is mostly disconnected and not doing much. It may be contributing to the generator warning light somewhat working.

The #2 terminal is OK to connect directly to the batt terminal of the alternator, it is how the alternator senses how much voltage is on the battery wire so it knows how much to output. That wire would normally be connected to the battery wire at some distance from the alternator, such as the point at which the wire connects into the main harness by the driver side headlight. If it is connected remotely, it gives the alternator a better idea of what is going on with the voltage in the harness so it can better regulate output. The #1 terminal is connected to a resistor wire in the cab or to a diode, and provides a way to turn the alternator on or off. It is called the exciter wire. If you have a warning light instrument cluster, this wire also (normally) runs the generator warning light.

Here's a thread that describes the setup with the diode, and also shows the wiring with the generator warning light, and talks about where on the harness the sense wire is best connected. http://67-72chevytrucks.com/vboard/s...d.php?t=604881

Re: Stock alternator to 12 SI alternator
 

Thank you...

Re: Stock alternator to 12 SI alternator
 

Thanks for this write up. I will be doing option 3. To be clear the alternator shown in your pic is for a 1985 riviera. I’d like to just do as you did. Also will it mount in stock location with stock brackets . I have a 1972 k10 running the alternator on the drivers side. 350 engine. Again thanks ja much

Re: Stock alternator to 12 SI alternator
 

Please check out the threads in my FAQs at the top of the electrical forum
http://www.67-72chevytrucks.com/vboa...d.php?t=815300