One wire alternator

I have "accidentally" ordered a 1 wire alternator. I put it in the cart on our Amazon account and my wife ordered a book..

So now I have coming my way a Powermaster 8-57141. That is their 150A improved ford black alternator with internal voltage regulator.

My dilemma is now - do I keep it or not? I am not worried about the cost, I know I can get a 3G for less.

As this model has a built in regulator I would just run a nice chunky wire to the battery side of the start relay and disconnect the ammeter and external VR. I guess I could replace the shunt and get the ammeter working again, but honestly that is the least useful gauge in the cluster so I am not worried about that.

Just wanted to get peoples opinions here.

I can't speak for the 1 wire, but I do like my 3G conversion and my converted ammeter to voltmeter gauge. I now have a useful gauge sitting in that pod. This is one of those mods that makes my truck far less the fire hazard too. Grateful to Gary and Jim for helping me along in that mod.  

I'm not a Powermaster alternator fan.  Big Blue had one when I acquired him and it failed soon thereafter.  Called Powermaster to get parts and was informed that they don't sell parts - you return the alternator to them for repair.  

I'm not into that.  I want to be able to get repair parts at the local auto parts if the thing fails while I'm on the road.  So now I'm running a box stock 3G.  But any 3G, even a souped-up one like Bill's 160A unit, would be fine because you can always drop another 3G in its place for the trip home.  Like maybe even from a salvage  Not true of the 1-wire Powermasters as you have to wire specifically for a 1-wire.

I'll let Scott/kramttocs persuade you that the Powermasters are the way to go.  He's the Powermaster czar as I think he now has three of them - inc my bad one.  Took me several years to find someone that would take it off my hands - for free.  

I have a Powermaster 1 wire. I think it's maybe 120 amps or so. No problems so far, I think I've had it the better part of a year.

If you are proposing that you run "blind" with regards to the health of your electrical system, and people have had problems with Powermaster failures, then I would think it advisable to get a gauge of some kind. I run a volt meter, so I should be able to tell if anything goes wrong. But my dashboard is not stock. So you could add a small round gauge somewhere (under dash or in the A pillar or something). Or you could get a small volt meter that plugs into your cigarette lighter. If you're just running around town and could make it home with a dead charging system, you probably wouldn't need it, but you could plug it in for a longer trip, so you could see a problem coming and start looking for a parts store. I assume you would keep the stock wiring in place so you could go back to a parts store unit if needed.

Thanks for the input everyone.

I will definitely leave all the original wiring in place. I may update some of it as needed.

The in dash ammeter is next to worthless, I will add a cigarette lighter VM though.

Gsmblue wrote

Thanks for the input everyone.

I will definitely leave all the original wiring in place. I may update some of it as needed.

The in dash ammeter is next to worthless, I will add a cigarette lighter VM though.

Mine doesnt even work, but I am trying to get Dakota Digital to do their RTX vintage look cluster for our trucks they have an actual volt gauge and it would be better in my book than pulling my cluster apart to send the ammeter out to be converted to a volt gauge.

I just stumbled on the "Rocketman" conversion page. That does look really interesting:

https://www.rccinnovations.com/index.php?show=menu-volt-all

When the Alternator gets here I will throw it on and use a cigarette lighter socket volt meter to see how it all looks, then I will prob do the switch from ammeter to voltmeter, looks simple enough.

I will document and add to the project thread. I think this will go down next weekend...

I have that exact RCI unit if you have any questions. One downside you have to send them your core ahead of time - he rewires the exact unit. Which is fine, but it means pulling your panel twice if you plan to drive the truck in the meantime. Also, he doesn't include wires, it's just the gauge and terminals. You'll need some ring terminals, crimper, and wire to complete the install.

One BIG word of caution.  Your new alternator is capable of kicking out 150A.  But my guess is that the shunt that feeds the ammeter is capable of handling about 75A.  So if you don't change the wiring, at some point you are going to melt that shunt and potentially catch things on fire.

As shown below, the shunt is between the output of the alternator and the battery.  So if your battery gets a bit low the regulator is going to tell the alternator to do its thing, and that shunt will not be happy.

Thanks Gary,  I am going to disconnect the ammeter and send it off to be converted to a voltmeter. That should take care of that.

Safety first!!

No.

Taking the ammeter out of the circuit does nothing for the shunt.  If you leave the alternator charging the battery through the shunt you have a very real chance of melting the shunt, if not causing a fire.

Let me say it this way: The shunt is not capable of carrying the full output of your new alternator.  You must take the output of the alternator to the battery and not through the shunt.

I encourage you to read the writeup on the Ammeter & Voltmeter tab on the page at Documentation/Electrical/<a href="http://">3G Alternator Conversion.

Two choices, can take and cut the shunt out and replace with a heavier gauge wire or you can do like I will be doing and take the OE charge wire and double it up with a larger gauge charge wire to a fuse that way the shunt will not be able to pass all the voltage with the doubled up wire.  I dont believe you can leave the OE charge wire off and run a new charge wire in its place if you can do this and everything function properly then I would recommend this route and tape up the terminal ends.

Understood. I will be running a new wire from the new alternator to the battery side of the starter relay. I will ensure the shunt and the old wiring is deleted as necessary and when I get a new voltmeter I will wire accordingly.

If I have any doubts, I know where to come!

I was very cautious when I did this on my truck last year, but then I don't consider myself real savvy in the electrical department. You're probably a lot less challenged than me there, but you might want to look over the following thread. As I stated above, Gary and Jim nursed me through this mod and I got exactly what I wanted and am very pleased in it.

 https://forum.garysgaragemahal.com/Help-On-3G-Page-tp86569.html 

Gsmblue wrote

Understood. I will be running a new wire from the new alternator to the battery side of the starter relay. I will ensure the shunt and the old wiring is deleted as necessary and when I get a new voltmeter I will wire accordingly.

Well, that will work.  BUT, you won't have left the old wiring intact so you can put a 1G in place of the Powermaster when it fails.

If you really want the ability to put a 1G in place of the Powermaster when you are on a trip, which I think is an excellent idea, then you don't want to remove the old wiring.  The shunt isn't a problem if you don't try to put more than, ~70A through it.

So I would put a 175A fuse on the fender liner some place and run a #4 or #6 wire to it from the battery side of the starter relay, and run the same size wire from the other side of the fuse to the 1-wire alternator.  Tape up the other wires for the 1G alternator so they can't short out, and you are done.

Your ammeter will only show discharge as it is now only seeing the load going to the cab from the battery/alternator.  But that won't hurt anything.  Then when you get the voltmeter from Rocketman you'll need to add a relay under the hood so the voltmeter isn't on all the time and draining the battery.  And you'll have to cut one wire and take it to the relay.  But it is simple stuff and you'll still have the original 1G wiring for when the Powermaster fails you in Timbuktu.

As always, great advice! Thank you Gary :)

Just don't want you to hurt that beautiful truck!  

The only reason I would not run any 1 wire ALT is in the AMC world some that have run the 1 wire have ended up with dead batteries after driving.

Because the 1 wire dose not get feed back from the battery it dose not know it needs charging and you keep pulling power out and not put anything back in.
If you were to open up the wiring (on AMC's) the factory sensor wire for the regulator goes back into the harness and not to the battery just for that reason.
The sensor wire on the 1 wires are done at the ALT inside IIRC
How can it know the battery needs charging as it sees it is putting out volts just not enough!

After seeing that on more than a few post I went with a GM type ALT with the regulator built in on my AMC but ran the sensor wire back into the harness to make sure the battery stays charged.
Dave ----

Gary Lewis wrote

Gsmblue wrote

Understood. I will be running a new wire from the new alternator to the battery side of the starter relay. I will ensure the shunt and the old wiring is deleted as necessary and when I get a new voltmeter I will wire accordingly.

Well, that will work.  BUT, you won't have left the old wiring intact so you can put a 1G in place of the Powermaster when it fails.

If you really want the ability to put a 1G in place of the Powermaster when you are on a trip, which I think is an excellent idea, then you don't want to remove the old wiring.  The shunt isn't a problem if you don't try to put more than, ~70A through it.

So I would put a 175A fuse on the fender liner some place and run a #4 or #6 wire to it from the battery side of the starter relay, and run the same size wire from the other side of the fuse to the 1-wire alternator.  Tape up the other wires for the 1G alternator so they can't short out, and you are done.

Your ammeter will only show discharge as it is now only seeing the load going to the cab from the battery/alternator.  But that won't hurt anything.  Then when you get the voltmeter from Rocketman you'll need to add a relay under the hood so the voltmeter isn't on all the time and draining the battery.  And you'll have to cut one wire and take it to the relay.  But it is simple stuff and you'll still have the original 1G wiring for when the Powermaster fails you in Timbuktu.

This is what I am going to be doing with the exception of I was thinking about doubling up the wires but I may just leave the 1G battery lug wire off and taped up since my ammeter doesnt swing either way.

FuzzFace2 wrote

The only reason I would not run any 1 wire ALT is in the AMC world some that have run the 1 wire have ended up with dead batteries after driving.

Because the 1 wire dose not get feed back from the battery it dose not know it needs charging and you keep pulling power out and not put anything back in.
If you were to open up the wiring (on AMC's) the factory sensor wire for the regulator goes back into the harness and not to the battery just for that reason.
The sensor wire on the 1 wires are done at the ALT inside IIRC
How can it know the battery needs charging as it sees it is putting out volts just not enough!

After seeing that on more than a few post I went with a GM type ALT with the regulator built in on my AMC but ran the sensor wire back into the harness to make sure the battery stays charged.
Dave ----

I dont like 1 wire for that reason, I have started up many cars at work with 1 wire alternators and they never hit the self excite threshold so the engine is running on just the battery.