Honda Car Forum

2nd Update, as I think now the charging system is operating normally.

"jim beam" <nospam@example.net> wrote
> does the voltage drop under load? you know, fans, lights, defrost etc.,
> on? if it drops to say 10V,

I checked. It drops to something between 11.8 and 13 volts *momentarily*.

> then you have a charging problem. if not,
> and it kicks up to 13/14V when loaded, everything's working just fine.

After the slight drop, it rises pretty quickly (3-10 seconds?) to something
between 14 and 14.5 volts.

When I turn off the loads, it stays up over 14 volts for a little while. (I
didn't wait for it to drop.)

If I then turn off the car, then turn it back on (no loads), the voltage is back
to about 12.7 volts (here in the summertime).

I can repeat the above events merely by turning on the headlights, though it's a
bit more dramatic with more electrical loads.

> the alternator should have a regulator circuit that determines whether
> it needs to "charge hard" or not. if the battery is charged and there's
> minimal load, the alternator is not required to produce max output, and
> indeed it shouldn't in order to not fry the battery.

I'm buying this.

My best guess as to what was happening in February (when unloaded, the battery
terminal voltage was 14.4 volts) is that it is somehow related to the
particularly cooler temperatures then compared to now.

> alternators generally fail when the diodes go. semiconductors have a
> limited lifetime at high temperatures, and hot climates and/or full
> electrical loads will keep them nice & toasty. oem alternators can last
> a good long time when treated conservatively.

Darn tootin'. I'm sure as heck not going to replace an OEM, dealer installed
alternator after a lousy five years and 50k miles... :-) That puppy better make
it to 100k miles or eight years, AFAIC.

I hope!

Autozone Aside: I drew on the "expertise" of the fine folks at Autozone today.
They did what they said was an "alternator test." The guy hooked up to the
battery terminals a sophisticated-looking electrical tester. (IOW, it does more
than my $15 Radio Shack digital voltmeter.) He read off voltages while operating
the throttle control manually (under the hood). He got the same sub-13 volts I
got. He never changed the electrical loads. His conclusion: Buy a new
alternator. My conclusion, "All he did was what I pretty much did, so not so
fast." I thought he'd at least take some readings at the alternator terminal.
But one gets what one pays for, I suppose. This check was free.

Firestone (where I bought my new Insterstate battery) aside: After buying and
installing (in the Firestone parking lot) my new battery Monday, I checked the
voltage and saw no change from my previous readings of about 12.7 volts. I
popped into the Firestone showroom and asked the guy if he'd give me his
opinion. He said I was wrong about the 14+ volts being usual when the car was
running. I said okay and left, not wishing to start a row and knowing this was
my problem, anyway. At this point, I feel the guy was speaking with some
legitimacy.

Lastly: Thanks, Jim.

Caroline wrote:
<...>
> John, I'm going to go work on cleaning up the battery cables,
> especially the ends, a bit more this afternoon.
>
> Mike, I'm looking into replacing as many battery cables as I can
> easily do. Some of these wire harnesses/bundles seem like a bit of a
> morass to get into. I guess there's an argument that (low load?)
> wires age with time and so should be replaced every so often,

No, there isn't! Wires in everyday appliances like cars and TVs don't
wear out. If anything, the insulation around the conductor can slowly
deteriorate and the terminals can go grotty but the wire is OK.

> but I
> wonder whether the amperage load through these wires is low enough
> that they tend to last a very long time. They don't see the same sort
> of load (via fatigue?) that spark plug wires see, I reckon.

There's a different kettle of fish! There is no wire in the plug wires!
What is there is a fluffy string soaked in (dry) carbon powder to act
as a very long thin resistor. When the string breaks, the cradle will
fallxxx (oops) the gap between the carbon ends saps the energy of the
spark leading to a weak spark.

So leave your wires alone except to check the connections and
clean/repair/renew as required.


--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.