Battery Charging

[Huw Powell]

> The alternator light doesn't tell you anything about the battery, it
> tells you the alternator is not charging the battery.  If the
> alternator is spinning and producing a current flow, the current that
> creates the magnetic field in the rotor is generated by the
> alternator.  If the alternator is not spinning, like when you start
> the car, the current to create the magnetic field is supplied through
> the alternator light.  The light switches off due to the magic of
> diodes and equal voltage potentials,

> 
> Any way of testing if the battery discharge light is really testing
> if the battery is discharging? Battery discharge light on dash tests
> voltage? Current?

So what iut *really* tells you is if the alternator is functioning properly.

And if it's not... you are discharging your battery to run the car.

If it's lit, two main culprits - worn, loose or broken alternator belt, 
or worn brushes in the regulator assembly.

Wiring/ground quality can also be an issue.

You can always set up an external voltmeter attached to the cig lighter 
or some such if you suspect charging/voltage issues are a problem.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/