Painless wire question

[Torkman66]

One wire alternator. Keeping ammeter. Does 915 black/yellow to alternator output and 916 black to battery side solenoid both have to be connected in order for ammeter to work?

 

[Oldtimer]

Yes, ammeter reads current the flowing thru wire between battery & alternator. . . which means the 915/916 wire needs to be large enough to handle all the current put out by the one wire alternator.
If the one wire alternator output is connected directly to battery (as most are), the ammeter will see no current flow.

 

[Torkman66]

Thanks. So I plan on connecting 915 to the same side of a maxi fuse (120 amp) as the wire coming out of the alternator. The other side of the fuse will go to the battery.
916 will be connected to the battery side of the solenoid and have its own inline fuse (probably a 60 amp).

Will this protect the entire system from a bad alternator condition (high voltage)?

 

[DirtDonk]

Just out of curiosity, how many amps is your 1-wire capable of?

 

[Oldtimer]

Not sure what Painless does to supplie power to fuse panel and key switch, but based on a stock Bronco harness this is what you will have.
If there is a dead short at the alternator, tha 120A fuse will blow, and the 60A fuse will blow a millisecond later.
The Ammeter will never show charge or discharge of battery, since 915 to 916 battery cable is a complete loop.
This is why a 1 wire alternator install usually involves converting to a voltage gauge.

You could do somthing like this if you want the ammeter to work, but I dont think 915 & 916 will be happy with 120 Amps of current when the alternator is at full output.

 

[Oldtimer]

When (if) I add a 1 wire alternator, I would replace ammeter with a volt meter, and modify stock harness like this.

 

[Torkman66]

Amazing graphics! I have a 100amp alt. Looking at your schematics and at the painless wiring diagram, I plan on connecting the Black 916 (which becomes black 972) to the battery side of solenoid through a 60 amp fuse. That will protect the fuse box. I will cap the end of 915 and not use it. I will run a 6ga wire from alt to 120 amp fuse then direct to battery. I know I will not have the ammeter anymore (not very helpful anyway), but will leave it in place for cosmetics. I already have a small digital voltage gauge set up with two usb charging ports inside the ashtray. So I will have volt reading if needed. Sound good?

 

[DirtDonk]

Just like oldtimer, I’m not sure how Painless routes their main charge cable either. So best to go by their recommended rating.
With the factory harness in good shape, you can use up to a 70 amp alternator with the ammeter.
With the Centech harness they claim you can use up to 100 amp alternator with the ammeter.
I thought Painless said limited to 60A. But I haven’t read the manual in awhile. Since you’ve got one in front of you, what did they say there limitation is?

Essentially, you can’t have it both ways. As Oldtimer explained, if you hook your alternator output directly to the battery, current, being current, chooses the path of least resistance.
Hence, all of your charge, or the vast majority of it will flow directly to the battery through the large cable and mega fuse. Little to none of it will go through the smaller charge loop.
Or maybe it works as a coequal partner? Flowing half-and-half? I don’t think so, but I’m not in electrical engineer.
Someone else will have to answer that.
You would still probably register a drain with the meter so when you turn the accessories on without the engine, it would reflect negative. But I think that, at the very least, positive charge readings would be very inconsistent.

 

[Torkman66]

Have most of the harness installed. Has taken a lot of time because I'm wrapping every wire/loom with the painless weave. It takes a lot of time to make the joints and tape off the ends. Overall coming out very nice. I went with connecting the 916 to a 60 amp fuse , capping the 915, and running the 100 amp alternator to a midi then to battery.

 

[DirtDonk]

Looks great!
Now here’s to hoping, you don’t have to change anything after it’s done!

 

[Torkman66]

So true! I’m wrapping and making everything pretty thinking the whole time how hard it will be to trace a problem. Couldn’t really test it first then wrap. That would also have been a lot of work. But I’m taking my time and doulble checking all wires as I go so hopefully all good.