Alternator Wiring

Here is a photo of my alternator. I don't know what model it is.

During clean up of all the unused wiring on the Jeep I traced the white wire to under the dash. The end of the wire was just hanging, I'm not sure what it was connected to. I gather this is for the indicator light, which my Jeep does not have now. I have an ammeter so I don't feel the need for a warning light. Is it normally necessary to wire this light to excite the field? I don't know if I've just been lucky that the alternator works as is.
Thanks,
Ken

 

Delco 10SI.

There's so much written about this online already. The white wire to #1 is the exciter, and it should connect to the ignition switch. It is meant to bootstrap the alternator into charging, and can also be used for an indicator light. It needs either a light bulb, a diode or a resistor in the circuit to stop (diode) or limit (bulb or resistor) back-feeding when you shut off the ignition.

(corrected, white #1, red #2)

 

Tim knows this but just made a slight error. #1 has the white wire on your alt.

 

Thanks for the info, it's helpful just knowing the model of alternator.

 

I used this diagram. Are they different? I’m starring to question my wiring job.

 

No they are the same. Where do you suspect your wiring is wrong?

 

Diagram A shows wire 2 as being fused and switched. Diagram B shows wire 2 as a solid connection to the positive battery terminal. My wire 2 is a solid connection. That's how I see most diagrams drawn.
This is what I see most often

 

I don’t see where #2 goes right back to Bat + without going to switch.

 

You guys wouldn't go round and round on this topic if you made the effort to understand the circuit.

It is useful to think of these devices as sources and sinks of current.

The big charge wire is obvious. It sources current to the battery (the sink) on demand. With an ammeter, it goes up to the dash, through the ammeter, and back to the battery.

#2 is the sense wire. It samples the system voltage and informs the regulator of how much current is needed from the alternator. The battery will pull down the system voltage (it's a current sink), depending on the amount that it's charged.

#1 is the excite wire. It connects to the ignition switch. At startup, it sinks current to start the alternator charging. Source flows to sink, lighting the alternator light, if present. When the alternator starts charging, terminal #1 becomes a current source. Source is now connected to source, and no current flows. The light goes out, if present. Turn the key off and the ignition is now a sink. Current then back-feeds to the ignition unless something blocks it like a light bulb or a resistance wire or a diode.

With the key off, the ignition is isolated from the battery, so the charge wire and #2 do not connect to #1 via their connection to the battery.

 

Note: I wouldn't connect a modern alternator to an old school ammeter under your dash (specially not with a jug of fuel under your butt)