[Benjamin]

My truck had a red 12 gauge wire coming off of the BAT terminal that went into a wire harness at the core support on the driver side. According to the wiring diagram this wire splits, one fork goes to the battery and functions as the charge wire, the other fork supplies the main power feed. If I disconnect this red wire and run a new heavy gauge charge wire, then the OLD 12 gauge charge wire becomes the supply path for the main power feed to the dash, and where it was originally intended to be downstream of the fork, it is now upstream. Also, you are now using the positive battery post as the main power distribution hub for the entire vehicle. So, I DO NOT want to do that.

Bottom line - Unless you are some kind of wiring wizard and you are actually going to do something that will improve the factory harness, keep that red wire coming off of your old alternator and connect it to the hot post on your new alternator. If you don’t you could be making things worse.


*Charge Wire sizing and battery charging requirements
How big of a charge wire do you need? Well, I guess it depends on 2 things.
One: how long will the charge wire be once you route it to your battery?
Two: What loads do you have on the charge wire, in addition to charging the battery?
I had an 8 ft piece of 8 gauge wire that was included in the Mad Enterprises goodie bag, so i did some quick math to see if that would work. Optima’s website says 1 to 12 amps is best for charging a lead acid battery, I have an Optima AGM, but whatever, i gotta get this done. I’m assuming I need to supply 10 amps to the battery to maintain it. As for the other loads, Watts / Volts = Amps, so 10A for my headlights (60W x 2 / 12V = 10A), 10A to charge the battery, and 3A for my HEI (don’t recall where I got that number) totals up to 23A, and my chart says 8 ft of 8 gauge wire is good for 60A, so this wire should supply PLENTY of current at the battery junction post. Also included in the Mad goodie bag was a 12 gauge fusible link and a nice non-insulated terminal which I put at the alternator end of the charge wire.

Right about now you might be saying “Hey Ben, are you headlights actually drawing from the junction post at the battery? Then why are you considering that as a load at that point?” Well, you are right, the headlights are drawing power from somewhere downstream of the “fork” that I was talking about earlier, which is fed by the 12 gauge wire coming off the hot post on the alternator, and furthermore, I am going to put my headlights on relays in the near future, so that I’m not routing that circuit all the way through the switch on the dash.

This seems like a good time to bring up the 1-wire alternator topic again.

If I had trashed all the wires coming off of the old alternator then I would have lengthened the main power feed by a good 6 feet, and through a 12 gauge wire at that. Now let’s look at some rough numbers and assume that we have about 6 feet across the front of the truck as that wire travels along the core support, then about another 4 feet from the turn by the driver side headlight to the firewall connector. That’s 10 feet for those of you who went to school in Shelbyville, anyway, my chart says 10 feet of 12 gauge wire is good for 20A, and I would be pulling everything through that 10 ft stretch of 12 gauge wire. Now the load to charge battery isn’t included in that, but we didn’t even bring up brake lights, turn signals, and whatever other accessories you may have scabbed on to your poor 40-year old wiring harness. I may be over-simplifying things, or I may be overlooking something else altogether. At the end of the day you may not have any problems with the 1-wire setup, but, it would be one step closer to an electrical issue.

*Idiot light- discussed below, if you want to maintain functionality of the warning light, you are going to need to connect it to the new alternator somehow.

*Voltage regulator - bypassed using home-made jumpers
Even though I am installing the one-wire alternator as a 3-wire alternator it is still internally regulated and I will need to bypass the original voltage regulator. I say bypass because I am going to use the blue and white wires coming off of the alternator. I want to be able to switch back to the original configuration, so to bypass the voltage regulator I made some jumpers to bridge the terminals at the voltage regulator harness using 16 gauge wire and male spade terminals. The blue wire gets bridged to the red wire which runs to the junction post near the battery. This wire is the voltage sensing function and it tells the alternator what the voltage is at that post. Since the blue-red wire is connected to the junction post at the battery, it is always hot. The white wire gets bridged to the brown wire and maintains functionality of the warning light, I guess to tell you if you throw a belt, or if your alternator quits charging. The white-brown wire will be hot when the ignition is on. Now white wire goes to #1 post on alternator and blue wire goes to #2. There are some alternative methods for bypassing the voltage regulator, but I did mine pretty close to the “Alternator Upgrade Wiring” thread as far as I can tell.