Electrical Problem w/ my 89 Honda Accord

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Do tell.
Well, it sure shows. Touch-of-bona-fide-class in writing and thinking...

I think my last line above, about agreeing with just "the essence" of what you said, is misleading. Let me clarify and just say all you presented makes sense to me.
You (and I guess Karl) are certainly right about checking connections, terminals, etc. Probably should have mentioned this to the OP, though there was a lot in his post that suggested he was alert to this and had cleaned and tightened, yada, when he got that 10 volt reading. Just seemed obvious to me that when he went from around 15 volts with the car running (which is high but maybe not unreasonable) to 10 volts with the car off, that that battery wasn't holding charge no way no how.
'course, speaking as an amateur, but I hope a studied one, I still wouldn't rule out further problems just yet, like I posted to his last post.
snip but comments all noted
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Elle wrote:

I think your assesment was totally correct and complete from jump. You don't have to clarify anything as it was spot on: If you see 15V with the car running and 10V with the car off, it most likely is the battery. Just like when you drive the car and hear "whompa-whompa" it is most likely a flat tire. Can it be something else? Sure but to first assume it isn't is just silly :)
Good call.
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snip
Can you be more specific?
.
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get weaker the battery voltage deteriorates, from failure to hold a charge and sometimes from shorted cells. Either way, failing batteries (or dead batteries) cause the alternator to put out maximum current for progressively longer times in order to bring the voltage up to the regulator level.
Alternators are odd things - by design, they will only put out so much current for a given field excitation. The ratings you see on alternators are those maximum ratings for about 14 volts on the field. The way that works is that the voltage they produce is proportional to rpm, and the frequency at which they operate internally is proportional to rpm. Since the stator windings are inductors, their reactance is proportional to the frequency (in turn proportional to rpm) so the maximum current the alternator will put out, even into a short circuit, is limited.
In the '60s, the alternator could put out the full rating (usually 35 amps) indefinitely. They were big, Tim Allen devices that scarcely ran warm at full output. Those days are long gone. Modern alternators are much smaller and are called on to put out much more current - often 60 to 100 amps. With a good battery, the electrical systems are carefully designed not to burn up and still keep up with demand. With a bad battery, the alternator runs too hot and cooks the insulation and the diodes. Eventually too much damage is done and the alternator fails.
Mike
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<snip>

Nice writeup. It's going into the FAQ.
--
TeGGeR

The Unofficial Honda/Acura FAQ
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