one wire alternator with functional warning light

[jimelfarm]

Been trying to find out how to make my idiot light functional with the one wire alternator. Any electrical guru's out there know a way?

[VetteVet]

Originally Posted by jimelfarm

Been trying to find out how to make my idiot light functional with the one wire alternator. Any electrical guru's out there know a way?

The alternator light grounds through the diode trio in the alternator and when the alternator starts charging, a 12 volt feedback to the light occurs, thus you have 12 volts on each side of the light element, canceling the ground and turning off the light.

The one wire alternator is self exciting and has no provision to connect the light wire (exciter wire), so it cannot turn off the light when the alternator begins charging. Since the light wire is now disconnected, the light will not turn on unless the wire is grounded. So you see you cannot have the light on and turn off unless it can see a charging voltage off the diodes in the alternator.

There are alternators made that work as a one wire or a three wire, which you could plug the exciter wire into if you had a plug adapter, and the light would probably work, but the alternator would not be a one wire so what's the point? You might as well convert to an internally regulated alternator and be done with it. The only difference between a one wire and a three wire is the regulator as far as I know.

Is the one-wire you have an SI style or the stock 10 DN style?

[VetteVet]

Here's the stock alternator.




This is the SI series most common as a one wire.



And here is the later style used after the mid eighties on most GM vehicles.
It is the CS style.



The SI and CS styles are internally regulated and are easily converted from the old stock alternator for a much improved charging system.

[Mike C]

I love 10SI alternators. And you can buy brand new Delco ones on Rockauto for about $60.

Then wire it up correctly with the charging light and the voltage sensing wire at the main fuse box. This extra length makes sure you get the regulated voltage at the main distribution and not just at the alternator which is how the one wire works.

[jimelfarm]

Originally Posted by VetteVet

The alternator light grounds through the diode trio in the alternator and when the alternator starts charging, a 12 volt feedback to the light occurs, thus you have 12 volts on each side of the light element, canceling the ground and turning off the light.

The one wire alternator is self exciting and has no provision to connect the light wire (exciter wire), so it cannot turn off the light when the alternator begins charging. Since the light wire is now disconnected, the light will not turn on unless the wire is grounded. So you see you cannot have the light on and turn off unless it can see a charging voltage off the diodes in the alternator.

There are alternators made that work as a one wire or a three wire, which you could plug the exciter wire into if you had a plug adapter, and the light would probably work, but the alternator would not be a one wire so what's the point? You might as well convert to an internally regulated alternator and be done with it. The only difference between a one wire and a three wire is the regulator as far as I know.

Is the one-wire you have an SI style or the stock 10 DN style?

It must be the SI style. It looks the most like the ones in the pictures. I know the idiot light isn't needed,just thought it would be cool to have. I can always hook up a volt meter,i suppose.
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[VetteVet]

Originally Posted by jimelfarm

It must be the SI style. It looks the most like the ones in the pictures. I know the idiot light isn't needed,just thought it would be cool to have. I can always hook up a volt meter,i suppose.
Posted via Mobile Device

If you have a plugin on the alternator, with two terminals, check it for 12 volts on the no. 1 terminal with the alternator on and check it for zero volts with the engine off. If you get those measurements then you should be able to plug the white wire into the no. 1 terminal and the light should work.

The problem is that the alternator is a one wire, internally regulated and your harness comes with an external regulator. This means that you will have to wire it like a converted internal regulator alternator and bypass the external regulator. This is easy to do but if you don't have the plug ins in the alternator it won't work.

Here's the conversion diagram in case you decide to get an internally regulated alternator.



The brown wire in the external regulator plug is extended to the alternator no. 1 terminal and the red wire in the external regulator goes to the no. 2 terminal in the alternator.

This diagram shows the two wires with fuses which are the battery gauge fuse power wires. You have the light so you won't have these two wires in your harness.