Why is my alternator working?

[i82much]

I noticed my aftermarket voltmeter reads a little low compared to the battery, especially when the fan is on high, so I decided to have a look at the alternator wiring. I don't quite understand, the alternator is unplugged but it seems to hold steady at the battery around 14 volts. Does anyone understand what is going on here?

Truck is a 72 K10, engine is now a 396. I bought it like this, so I can't say much about the history. Where is the main junction usually located on these trucks? I would like to get the wiring correct, have the charge wire going to the main junction through a fusible link and a charging wire from the junction back to the battery with another fusible link.

Thanks!

[franken]

See that big red wire? That's where power comes out.

[i82much]

Originally Posted by franken

See that big red wire? That's where power comes out.

yep, i get that. but i thought one of the two wires on the plug was for voltage sensing, and the plug is not plugged in? so how does the alternator know whether to charge?

[57taskforce]

Looks like a gm one wire alternator to me. It's internally regulated and capable of sensing without the plug.

[i82much]

Originally Posted by 57taskforce

Looks like a gm one wire alternator to me. It's internally regulated and capable of sensing without the plug.

there we go. i did not realize there were delco one wire alternators, i thought only the aftermarket performance companies and such made them.

if i want to go back to a three wire, can i just remove the black plug and put the connector back in? assuming the two wires to the pigtail are ok, i mean

[57taskforce]

I went with A delco 10si on my k20. All I had to do was jump a couple wires down in the factory external regulater harness. It bolts in and the plug worked just fine.

[i82much]

Originally Posted by 57taskforce

I went with A delco 10si on my k20. All I had to do was jump a couple wires down in the factory external regulater harness. It bolts in and the plug worked just fine.

I did the same years ago on a 65 GTO. Too many years ago, as a matter of fact!

[garyd1961]

If it's working why not just leave it alone, 14 volts is pretty good.

[i82much]

Originally Posted by garyd1961

If it's working why not just leave it alone, 14 volts is pretty good.

I will, for now. Eventually I will go back to a three wire with the sensing wire at the junction.

Oh, yeah - where is the main junction on these trucks? Where did the factory sensing wire come from?

[clay68c10]

I think the sensing wire goes to the horn relay, most 60s GM stuff is that way as I recall.

[i82much]

Originally Posted by clay68c10

I think the sensing wire goes to the horn relay, most 60s GM stuff is that way as I recall.

Got it, thanks.