<theo.chan@gmail.com> wrote
> Interesting post;
>
> I noticed the exact same problem crop up last week on my 1990 Honda
> Civic wagon. The red battery light on the dash would flicker
> intermittently ont the highway, and sometimes stay on as long as 5
> minutes. The battery is about year old. Now that I am back in the
> city, it may flicker a bit and come on for about 10 seconds.
>
> After a voltmeter test, it shows that the alternator is charging the
> battery fine when the engine is running, but under full load (radio,
> heater, defroster, lights), it is not. Is this something I should be
> worried about?

Can you do the five quick and dirty voltage checks at the site
http://home.earthlink.net/~honda.lioness/id13.html and report back?

The voltage is supposed to drop, by design, when you add the loads you list.
The question is how much it is dropping.

Regardless, as you'll see from the commentary at the site above, your
alternator system is highly suspect at this time.

If it's the brushes (and based on posts here, I think that's a very high
likelihood for a car your age), then I would get them replaced as soon as
possible. For one thing, I think the car could leave you stranded any day
now. For another, the condition is going to worsen until the battery does
not charge fully. This does lower the battery's life.

Can you share the battery history of this car, including jumpstarts over the
years? Is the alternator the original, with original brushes?