On Jan 27, 10:26am, Scott Turner wrote:
> Subject: Alternator, Again
> Well, the new (rebuilt) alternator I put on the MGB performed well for
> about two weeks and died. I just sent it off for exchange. As with
> the old one, this one was only producing about 11.5 volts, and so the
> battery was not getting charged.
>
> Is there something that can kill alternators?
Yes. A shorted cell in your battery. 11.5 volts just happens to be 5/6 of
13.7 volts, which is the voltage the alternator is trying to get the battery
up to. You may even have replaced the battery recently, like just before the
alternator died. But it still may be bad. Quite often, a dying alternator
can take a battery with it, and vice-versa.
How do you tell if your battery is bad? First, charge the battery with an
external battery charger overnight. Disconnect the battery charger, wait a
half an hour and measure the battery voltage. You should measure a voltage of
2.1 times the number of good cells in the battery, normally 12.6 volts. If
it's 10.5 (or 8.4 or ...) you have (a) shorted cell(s) -> replace battery.
Wait a couple of hours and measure the battery voltage again. It should be
*the same* as the first measurement you took. If it's lower at all, one or
more of the cells have a self-discharge problem -> replace battery.
Better do this before you put another alternator in. They won't keep
exchanging 'em if you keep toasting 'em. :^)
Pat Vilbrandt John Fluke Mfg. Co., Inc. Everett, Washington USA
UUCP: pwv@tc.fluke.COM or: { uunet, uw-beaver, sun, microsoft }!fluke!pwv
ARPA: fluke!pwv@uw-beaver.ARPA
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