New Battery doesnt charge off of new alternator, 77 300D

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james.freire@gmail.com - 02 Mar 2005 20:01 GMT

Hi All,
I have a 77 300D where I have been having a problem where the battery
is not getting charged from the alternator.
I replaced the alternator and the battery still does not recieve a
charge (I test using my multimeter). The battery is brand new and
fully charged. I replaced the alternator as I should have, making sure
the battery is disconnected when plugging the altnernator plug into the
alternator and yet my battery is still getting drained.

I have tested the continuity from the battery to the alternator plug. I
hooked my battery up while having the alternator unplugged. I put my
multimeter in the terminals of the alternator plug and had a battery
charger on my car battery and was able to get voltages from 12.2 all
the way up to 13.8.

Upon reading the schematic I see that the positive lead from the
alternator goes to the starter and then to the battery. Could there be
a problem with my starter that is preventing the battery from getting a
full charge? The starter does operate perfectly though.

Thanks for any help anyone can give!

-James

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Richard Sexton - 02 Mar 2005 21:15 GMT

Did you replace the voltage regulator when you replaced the alternator
or did you use the old one?

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james.freire@gmail.com - 02 Mar 2005 21:26 GMT

The electrical diagram for my car says that it has an internal voltage
regulator and the alternator i purchased, a bosch AL80X also states
that it has an internal regulator.

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Richard Sexton - 03 Mar 2005 00:10 GMT

>The electrical diagram for my car says that it has an internal voltage
>regulator and the alternator i purchased, a bosch AL80X also states
>that it has an internal regulator.

Internal is an odd choice of words for the thing that bolts on the
back, I'd have called it "integrated" but no matter...

You're leaking electrons someplace and you have to find the leak. Get
a volt meter and see if they're at te alternator, then follow the wires
and see where they're leaking out. Could be a ground issue too, if you
haven't taken off your ground connections, cleaned them to within an
inch of their life (must be shiney) and put them back tighty with
conductive grease in recent memory then you should probably do this too.

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William P.N. Smith - 02 Mar 2005 23:43 GMT

>I replaced the alternator and the battery still does not recieve a
>charge

When you say "new alternator", do you mean factory fresh, never been
in a car before, or do you mean rebuilt? My experience with rebuilt
alternators has been pretty dismal, rebuild seems to mean "Replace the
brushes, slap on a new coat of paint, and ship it back out." Last
alternator I replaced I went through 3-4 of them, till the auto supply
place got sick of my saying "Nope, try again" and allowed me to use
their tester to find a good one.

[Same thing with rebuilt starters, but that's another story.]

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Ernie Sparks - 23 Mar 2005 04:18 GMT

Since the alternator is putting out proper voltage your problem is a drain
somewhere else. Disconnect the ground cable and put a multi-meter between
the ground post and the ground strap. You shouldn't get any current flow if
everything is off. Make sure you don't have a hood light that comes on when
the hood is raised. I've known of glove box lights and trunk lights that
have drained batteries causing a lot of headaches. This is simply a matter
of isolating the drain. Also, some radios cause a small drain all of the
time as well. This shouldn't be a cause for concern with a new battery but
start checking everything. Good luck!

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