71 Charger, 383 auto.
Dash guage needle favors the "C" side of the middle mark and the hand held multimeter reads 13.4 at battery terminal when idling.
When I turn on the head lights, the dash guage pulls down to about 1/8-inch into the "D" side and the multimeter reads 12.0 at the battery.

Why such a load from turning on the lights???

Could it be a bad battery?
Are there any components in the "lighting-chain" like sensors, relays, or switches that could contribute to such a draw?



Thanks everyone!

Idle RPM? Check all the grounds.

Typical Mopar, mine does the same. You may consider running your headlights through a rely. Check bulkhead connectors for corrosion too.

yes thats is because because the Low output given by the Mopar alternators that are unable to charge at iddle, making suck the power from batt.

The problem then becomes that when reving up, the charge output from alt is increased for long time and high peaks, burning everything.

what we do need is an alt able to feed the car all ( or mostly ) of the time, to save from discharge ON REGULAR CONSTANT FUNCTIONS like headlights, Radio and A/C blower. Then won't care to get a slight discharge when pressing brakes or turning lights, or lifting windows on power windows setups because all of these are just momentarily discharges, not constant.

here is a pair of good readings with some nice upgrades... first one is the one I have right now, and I'm PLENTY HAPPY with it working with an stock later Mopar 60 amps alt:
http://www.dodgecharger.com/forum/index.php/topic,33574.0.html

I would say that upgrade is PLENTY safe still with 80 amps alt because iff you are needing in some moments full 80 amps from alt is because car demand from splice what is BEFORE AMMETER. Is hard that batt needs full alt charge output to get it full charge back so I don't think you'll get 80 amps going through ammeter ever. Then if you want more alt output, even that will work too, there are safer ways to make it:

http://www.dodgecharger.com/forum/index.php/topic,61947.0.html

both are to keep ammeter working since IMHO is the more reliable and realtime charging status gauge reader. BUT IS TRUE that needs to pay attention on condition of all the charging system before keep the amm working.

There are also couple of good discussions we got around on moparts that I think I could dig to you.