Hi,

It seems there is a shortage of people wanting to put their “two cents” worth into answering your concerns.
Maybe it has something to do with the coin shortage nation wide.
This happens when the economy goes south and hurts consumer confidence. The metals market gets a boost in confidence as being a standby currency instead. The outflow of “fiat money” being printed up and sold has gotten ridiculous.

The warning light is nothing more than a resistance put into a circuit that feed “exciter current” to the windings of the alternator. It just happens that a light is there to burn off that some excess current instead of it just being heat. The rest moves on to the alternator.
The light or current from, it must have to have a way to be turned off, if the alternator is not being used to charge or the battery will drain down through the regulator.
When there is enough current brought in, to create a magnetic field in the windings, that current, then, moves outwards through some exciter diodes. It starts feeding the alternator system and the regulator watches the load side and regulates the current output by tenths of a volt.

When this is all happening with the rise in voltage or current starts an opposition to the incoming current from the warning light. The voltage will always be lower than the output that you read with your meter.
In fact even if the light get opposed, just a tiny bit, the light goes dim or out and in that case it’s a false indicator. It then gets called an “idiot light.” You just don’t know what it’s really doing!
A dash voltage meter is the best diagnostic indicator as it tells how much and when!

It’s not exactly rocket science, once you relate it to something in life you see everyday. More of something, move towards, the less of something. Heat goes to cold or the heavy end of seesaw shifts things!

What you are doing is fine, except you got to disconnect the exciter inputs when not in use.
The reason you had to drive around awhile and then it would start charging is the fact that diodes do have some amount of leakage or seepage. Their not 100% at clamping voltages.
The exciter or warning light circuit cuts to the chase around doing things.


Two alternators are usually used separately or an alternator can be built into one with two outputs.
Those have isolated outputs so each “load circuit” will be charged evenly and does not drain the other.
Other wise, it’s one big load being watched by as many as you want to be watched by.
Like those in motor coaches, one will keep the engine starting side isolated from the home needs.
If you use an isolator between them.
I can cross mine together with an auxiliary starter solenoid, in emergencies or desperation, if one side get too low for various reasons.

I’m curious why you are racing with twice the charging capacity?
As when in racing, don’t you try to be bare bones everywhere?

Phil