batteries, alternators, etc

[Brett Dikeman]

Okay, finally decided to poke around the charging system since I've
always suspected something isn't quite right.

Off, car not run in several days, battery voltage is 12.5, I believe.

Start it up, voltage at the battery is 14.0 and climbs slowly over
several minutes to 14.1; dash gauge agrees.

Let it idle for several minutes while I poke around here+there,
checking for voltage differentials between the terminal+clamp on each
side, checking the voltage between battery and jumper post.

I had a lot of trouble getting good connections at both terminal and
ground up front, but voltage up front was -very- close to voltage at
the battery terminal(s.)

Kick on the accessories; rear window defogger, headlights on high,
etc.  Engine slows down a teeny bit. Check voltages again.  Much,
much lower; not much above battery voltage, in fact; 12.8 or 12.9 I
think; dips occasionally, but probably due to the bad connections
between test leads+post/ground.  Same at the post, to within less
than a half tenth of a volt.

Turn the car off, leave headlights on etc; measured voltage drop
between terminals and clamps, and it's VERY small on the positive
clamp(we're talking maybe a few tenths of a mV, the Fluke seems to
have an error range larger than what I measured :), none on the
ground.  Might clean it up, dunno.


This is either a rebuilt or new alternator(don't remember which),
installed within the last 2, maybe 3, years.  Battery(exide) is at
least 4 years old and levels were recently checked.  A few white
specs of battery fluid here+there on top etc.  Terminals looked
pretty good.

This summer, the alternator seemed to -barely- keep up with the stage
2 fan, and once when stage 3 came on(waiting in a parking lot, hot
summer, AC on) I had to take the car around the block because I was
afraid the battery would totally give out and/or car would overheat.

Comments?

B
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