HO alternator recommendation

I have a 65 mustang and have looked into the one wire type of alt. These older cars didn't use that much voltage. I'd research the one wire alt and then your options open up a bit. it will also clean up a few wires from under the hood. Or you can look into a capacitor for the stereo and controller/ relay for the fan.

I maybe a little wrong electrical is not something I am that great with.

Good Luck

Feels like I'm the only one on the forum these days. 😄 Guess I respond to myself to document where I'm at and maybe help someone else get at least this far.

I've been researching this topic and I'm convinced the 1-wire GM alternator swap would work - as would the Datsun alternator mentioned above - with some minor rewiring.

...EXCEPT for the ammeter gauge. The ammeter guage creates a potential fire hazard if you upgrade the amperage of your alternator. I haven't figured out how to work around it yet.

The problem is this (as far as I understand it):

The ammeter guage is wired in series with a shunt and measures the flow of current. Hence with thr car off and lights on, it measures negative flow as the truck draws from the battery. Start the truck and it registers positive flow.

As you increase the power produced by the alternator, it registers higher on the ammeter guage. The 1-wire alternator turns itself on and off, only generating power when needed (so far so good).


If the battery is low, the alternator produces more power. With the stock alternator, it can only make so much power at once. If you have a more powerful alternator, it can produce too many amps for the ammeter shunt to handle ...and melt it.


It sounds like you might get away with it for awhile, depending on your electrical draw. The risk is mostly if you draw down the battery for whatever reason - then the alternator will pump all those juicy amps back into the system to charge your battery.

It can also be an issue if you use a lot of power at once. For example, your lights are on, you're listening to music and you convert to an electric cooling fan.

That last one is the whole reason I want a higher output alternator - so if it creates risk of catastrophic failure, then the project is a non-starter for me.

I think you can bypass the ammeter, but I don't know enough about how to do that yet. Then your ammeter won't work, but you don't need it anyway with a modern self- regulating alternator.

HOWEVER, even that won't work for me. When I finish restoring my truck it will need to pass an inspection. All the guages must work or it will fail.

I read some hotrodders suggesting you can convert your ammeter to a voltmeter so you're not left with a dead gauge - but then let's review where we're at:

1. Learn to rebuild the dash to replace the ammeter gauge with a voltmeter, so you can bypass the shunt.

2. Bypass the shunt so you can install a higher amperage alternator.

3. Install a higher amperage alternator so you can install an electric fan.

4. Install an electric fan.

... this is a lot of steps just to get to the fan I'm really after.


On the plus side, the 1-wire alternator sound stupid easy to install. After you get it mounted and a belt installed, you just run the one wire to your battery - or the positive on your starter. That's it.

So it's not really the alternator that's the issue. It's that the truck can't handle the extra juice. Likely there's some safety margin - but how much? Do you want to try a jump from 35 amps to even a modest 60 on a 50 year old vehicle?

An easy bolt-in solution to the lack of a battery light is the american-autowire "11 VOLT ALTERNATOR WARNING LIGHT MODULE".

It's a prefabricated low voltage sensor that illuminates a bulb anytime it senses 11 volts.

I've read of a few people making their own, but I'm still investigating how. This takes the guesswork out of it.


I think I'm getting back on track now... That means:

1. Install a new alternator - either a 1-wire or 3-wire.
2. Bypass the ammeter by connecting a large gauge wire from the Alternator to the battery or starter positive stud.
3. Install a low voltage sensor and connect it to the light in the gauge cluster (if the truck has one - add one if it doesn't).
4. live with an ammeter that still may show if the electrical system is in a state of charging or discharging, but may barely register any changes.

I can see no easy way to make the ammeter work short of swapping the ammeter gauge and shunt for ones designed to handle greater load - and if you can do that, it would be better just to swap to a volt meter since you now how an internally-regulated alternator. Basically, if you're comfortable with gauge-cluster surgery, might as well eliminate the ammeter altogether.

Also, although the "1-wire" alternator is easier to install, the 3-wire alternator is supposed to be better. On a 3-wire alternator, the main lug on the alternator is the same as it is on a 1-wire alternator - it's what's pumping out the power. You would connect it just as you would for a 1-wire alternator.

The two other wires are the "excitation" wire (though from what I'm reading, that's actually kind of a misnomer - but I digress...) and the voltage-sensing wire.

I don't actually understand the benefit of the excitation wire. Some of what I've read suggests that without it, the alternator doesn't start producing power until the first time it spins up over a certain speed - but I think there are "1-wire" alternators available that don't have that problem. There's no disadvantage to this wire though - other than having one more wire to connect to switched power.

The significant change is the addition of the voltage-sensing wire. It connects to your junction box (i.e. where all your car electronics connect to draw power). Based on the voltage at that location, it tells the alternator to make or stop making power. Without it, the 1-wire alternator is measuring voltage at the alternator to make that determination - but the voltage drop at the junction box is more accurate. Basically it helps avoid voltage sag that might otherwise result in dimming light or poorly-performing electronics related to the 1-wire alternator not adjusting to power draw as well as it could with a voltage-sensing wire.

Circling all the way back to the alternator at the top of this thread, I ASSUME it's a 3-wire model that works like the GM 3-wire alternator I've been describing. All this research relates to the GM 1 or 3-wire alternators, but I assume alternators from other brands likely work the same way. However, I'm not totally sure because it doesn't label what the wires are for. It just says connect one to switched power and the other to "12v post".

The switched power wire sounds like the excitation wire (you only want to "excite" your alternator when the car is running). The "12v post" wire though... if it's telling you to connect to the 12v battery terminal, then it wouldn't be sensing the voltage at the right place. If it actually is a voltage-sensing wire, then it would still work, just not as well as it could if you connected it at the junction box... or maybe THAT'S what it means when it says "12v post".