Don't do it.

One-wire alternators are harder on batteries, and because they don't have remote sensing, they can't read the voltage at the bus - just at the battery. That means you get more flare from your headlights and such, and it's much less stable voltage, which is a big deal for sensitive electronics.
With a one-wire, your alternator light won't work.

And adding insult to injury, it costs more.

3 wire alternators are not complicated. Yes, it's two more wires - but you can do this! You can count to three. Your car is set up for it! Get a good 3G alternator, spend less, enjoy it longer, and call it a win.

 

Don't do it.

One-wire alternators are harder on batteries, and because they don't have remote sensing, they can't read the voltage at the bus - just at the battery. That means you get more flare from your headlights and such, and it's much less stable voltage, which is a big deal for sensitive electronics.
With a one-wire, your alternator light won't work.

And adding insult to injury, it costs more.

3 wire alternators are not complicated. Yes, it's two more wires - but you can do this! You can count to three. Your car is set up for it! Get a good 3G alternator, spend less, enjoy it longer, and call it a win.

I purchased a complete wiring harness for a 1968 Mustang from American AutoWire and it calls for a one wire alternator to be used. It has nothing to do with me thinking the factory 3 wire is "complicated" lol.

Anyways I will be running aftermarket gauges with a voltmeter and will not be using a factory gauge for the alternator.

 

I've had a one wire alternator which is believe is a Powermaster (can't remember) since 2009 and have put close to 40k miles on it. Have had no issues with it. I think the reason I went this route was that I was starting from scratch, otherwise I'm not sure why I didn't just go with a 3G which may be what I get to replace it should it crap out. I've also noticed almost no voltage fluctuation on the Autometer gauge. I'm not sure what flare from the headlights means. Flickering maybe? Haven't noticed any problem with the headlights either but they are on relays.

You should be able to use the same alternator on a 351 provided your mounting isn't different for some reason.

 

I've had a one wire alternator which is believe is a Powermaster (can't remember) since 2009 and have put close to 40k miles on it. Have had no issues with it. I think the reason I went this route was that I was starting from scratch, otherwise I'm not sure why I didn't just go with a 3G which may be what I get to replace it should it crap out. I've also noticed almost no voltage fluctuation on the Autometer gauge. I'm not sure what flare from the headlights means. Flickering maybe? Haven't noticed any problem with the headlights either but they are on relays.

You should be able to use the same alternator on a 351 provided your mounting isn't different for some reason.

If you run a voltmeter off the bus and compare it to the voltage at the battery, you can see a significant change in voltage when you turn accessories on and off that are connected through your fuse panel. One-wire alternators only sense drain coming direct from the battery. As a result, you can sometimes see something like a 2V drop at the bus itself. Primitive electronics like the electric wiper motor, heater blower, and turn signals won't care much. But a new electronic radio would.

As you're driving, if you have the headlights on, as the alternator cycles on and off, it is usually unnoticeable if your wiring is fine, and you have a 3 wire alternator. But with a 1 wire, most cars will experience a situation where the headlights brighten, then dim, then brighten as it kicks in and out.

The ability to sense voltage at the bus directly is kind of a big deal on a 3 wire alternator, and it allows a much more nuanced approach to feeding voltage as needed, rather than a "BAM! I'm ON!" charging situation.

To be clear - this is not a 'hate' issue. It's just a simple matter of "this one's better in every way and costs less". Seeing something that is appropriate for a tractor applied to an otherwise high-tech and well thought out restomod always leaves me shaking my head. It's a matter of ignorance, not one of "well, I like this one more!"

 

a. Do you NEED 150 amps?
b. Do you have an ammeter or warning lamp?
c. Do you have a single V-belt alternator drive?
d. Do you NEED 150 amps?

 

I purchased a complete wiring harness from American AutoWire for a 68 Mustang and it calls for a one wire alternator. I will be running aftermarket Autometer gauges with a voltmeter. I want to run electric fans, aftermarket stereo and possibly other stuff that never came from the factory as well.

 

There seem to be few more polarizing debates among Mustangers than one wire alternators. Some like them and others really, really hate them. I’m not quite sure what has produced that level of dislike but it is what it is.

I have a one wire on my ’70. It did quite charging about three months ago. I sent it back to the manufacture and they returned it with a second wire (so now it is a two wire) under warrantee. The problem turned out to be that the “self energizing” feature had quite working so it wouldn’t start charging. I suspect that if I had been able to energize it then it probably would have charged. The second wire is a small gauge wire (connected to switched power) that now excites the fields and it charges as it should.

Back in the ‘70s I build a one wire alternator out of an old GM Delcotron alternator. I used that for years with out any noticeable down side. Back then a 60 amp alternator was an upgrade. If you want more amps buy the alternator. I don’t see any disadvantage other than cost. If you can foresee adding more electrical components at some later date such as large electric fans, an amp for your sound system, etc. now would be a good time to build in some room to grow. On the other hand, if you think you might want to return to a concourse correct car at some point, then don’t.

Art.

 

My suggestion is to just go buy a 3G alternator from a 95 Mustang Gt.

 

This is why I love this forum, i am always learning something!
I bought my 70 in 2019 with from what I can tell a Power Master 1 wire alternator.
It also came with FiTech fuel injection with Fuel Commander, Dakota Digital VHX gauges, electric fan, and I added Vintage Air AC, would this 1 wire set up cause issues with these electronics? What would symptoms be?

 

1 wire alternators are horrible. They are appropriate for tractors and not much else. I am going to post my usual must-read alternator link here when thinking about upgrading/changing alternators:

BillaVista.com-Alternator Bible Tech Article by BillaVista

Everything you could ever want to know about alternators...the advantages/disadvantages of the various types of alternators. The long and the short of it when it comes to 1 wire alterantors is they have zero advantages and multiple disadvantages. If you put all the wires in the same loom, you can't even claim a 1-wire looks cleaner. Anyway...read the link and understand before buying an alternator.

 

I’ve been using a one wire Powermaster 150 amp alternator on my car since 2017 and it has yet to experience flickering lights, wiring meltdowns, or other issues noted above. It uses a single V belt pulley as well. My electric fuel pump, dual electric fans, and fuel injection drove me to an increased amperage device.

Perhaps my curved Monte Carlo bar, rear disk brakes, and 17” wheels are warding off the evil ju-ju threatening me and my car?

 

I’ve been using a one wire Powermaster 150 amp alternator on my car since 2017 and it has yet to experience flickering lights, wiring meltdowns, or other issues noted above. It uses a single V belt pulley as well. My electric fuel pump, dual electric fans, and fuel injection drove me to an increased amperage device.

Perhaps my curved Monte Carlo bar, rear disk brakes, and 17” wheels are warding off the evil ju-ju threatening me and my car?

My biggest problem with 1-wire alternators is their propensity(not exactly the word I am looking for here, but the one I can think of) to overcharge a battery with a low state of charge...and the fact that self-exciting alternators tend not to actually "excite" without a slight rev of the engine to get the field operating. IE: directly after starting a self-exciting alternator takes more RPM to start charging whereas an external field wire alternator will start charging as soon as the engine is running and even generate current during cranking

 

I'm curious if those that have noted the potential problems with a 1-wire alternator have actually experienced these issues themselves and, if so, was the alternator installed per the manufacturers instructions? A 1-wire alternator does sense voltage, it just does it with the same wire that supplies the power. That charge wire needs to be sized per the manufactures directions and is usually much larger than you would typically use. My 160 amp Powermaster requires a 4 gauge power wire as well as a 4 gauge ground wire. That charge wire can go to a power buss that is connected to the battery and doesn't have to only go straight to the battery. The very large power wire from the alternator insures that full alternator output is available at the buss. Alternatively, most Powermaster "1-wire" alternators have the ability to instead be wired conventionally.

 

Unless you use some kind of rectifier, dumping an alternator's output to the bus directly results in a very 'lumpy' 14V system, not smooth DC power. Some electronics are robust enough not to care about that, but others would definitely experience problems. Running output to the battery directly, but sensing from the bus separately has a lot of simple and inexpensive advantages.

 

In answer to jef@’s question,

I’m running a Mechman 170 amp one wire, now two wire, alternator on my ‘70. I have a custom six gage dash with Autometer analog gages including a GPS speedometer. I have not noticed any thing with the gages that would look abnormal. But, I’m carbureted, no FI, and not digital gages, so if that makes a difference, I can’t offer any help.

Art.

 

I went to a u-pull-it and got a 3g out of a late 90’s v6 mustang with all of its wiring for $40. You may have to change a pulley or clock it, but I didn’t need to for my serpentine set up on my 5.0 roller motor. Worked awesome.

 

My recommendation for a 1G replacement? DB Electrical 95A small-case 3G. Pretty much a "bolt-in"..... requires a pulley change as it comes with a multi-rib pulley to go back to a V-belt. Preserves the function of your factory alternator warning lamp and ammeter.

 

Seems like a good option as well.

 

As for the amperage I'd say you probably don't need more than a 95 or 100 amp alternator, unless your running electric fans and a stereo with amps etc.

 

For those that do not know, you can technically convert your 3G alternator to a one wire set up. You just replace your voltage regulator on the 3G alternator.

In this set up the "exciter" wire (green wire with red stripe) is removed and the alternator becomes activated when certain RPMs are achieved. I have this on my set up. My EFI control module displays 12.3 volts when I start the car and gives me a yellow warning banner to indicate volts are too low. I blip the throttle and volts go up to around 14.2 and the yellow warning banner goes away after the alternator activates.

So in this set up you only need to hook up your charging wire.

I believe my charging wire is 4 gauge (Below instructions say 6 gauge minimum). My system is no where near stock. Completely custom, but I used this wiring diagram as an example for my system. So, other than the green and red wire not being there my system is set up like the below diagram. Besides blipping the throttle to get the alternator to come on it works flawlessly. Very happy with this set up on my car.