Alternator "L" Terminal Question and EFIS Input

[cfiidon]

I've read the forum posts and helpful schematics for the ND alternators but I am still not certain of the "L" (lamp) circuit operation. Some explanations seem to indicate that when the alternator output stops, the L terminal goes to ground, enabling an ALT lamp to light, as the lamp has battery voltage on the other side. Great.

Some literature I've read seems to indicate it has a voltage on it. When it matches the battery voltage the lamp doesn't glow, when the voltage drops a bit (as in a slipping alternator belt) the voltage on one side drops a bit allowing current flow and the lamp will glow dim.

The bottom line is this: If the terminal really does go to ground I'd like to connect it to my Dynon D180 general purpose inputs and label that function as "ALTERNATOR OUT". But before I do that, I want to know the actual function. Anyone know? Anyone used it as an input to an EFIS or EMS.

Yes, I know I could install lamp, but I don't want to. I can also simply rely on the warning when the amp shunt value goes below a certain value, and that may be the easiest.

Don