Date:         Wed, 2 Dec 2009 12:56:59 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: need advice on charging light coming on in my 90 Vanagon GL
Comments: To: Mtbdavid2@AOL.COM
In-Reply-To:  <d28.5aadff1e.38476d5c@aol.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 02:12 AM 12/2/2009, David Cohen wrote:
>  During the tail end of a 6 hour trip back from Turkey Day and  family
>bonding, my charging light came on.  I recently had a pretty large  car stereo
>amplifier and high power car stereo installed.  I also purchased  a black and
>decker can cooler than plugs into the lighter socket.  So, I  had my car
>stereo running, the can cooler and cell phone plugged in to the  lighter
>socket and drove this way for about 5 and half hours and then
>my  charging light
>came on.  The can cooler has a auto shutoff when sensing a  low battery
>charge.  The can cooler shut down at the same time the  dash
>charging light came
>on.   Oh, I also had turned on the  headlights for the last 2 hours of the
>drive home.

Headlights ten amps low, ~twenty high; double that if you've got
funny bulbs installed.
Running lights ~3 amps, maybe six if you have funny bulbs in the taillights.
Heater fan, twelve amps on high speed.
Can cooler four and a half amps.
Cell phone an amp or less.
Stereo anywhere from five amps to infinite, depending how ridiculous
you've gotten and how loud you play it.
Engine/ECU/fuel pump under 25 amps, probably under 15.

So conservatively you're drawing 30-35 amps going down the road.
Add wipers, rear defrost and heater fan, 45-close to 60 depending on
blower speed.

If your stereo averages more than 20 amps you've probably gotten
beyond what's reasonable to expect from a 90A cold-rated alternator,
which I'm guessing at around 80 amps.

13.5 v at the battery isn't a very good charging voltage, shame on VW
for not using a sense wire to read voltage at the battery instead of
inside the alternator -- BUT that has little to do with your present
problem except that the battery likely wasn't at full charge to begin with.

Slipping belt not unlikely but you ought to hear it, it sounds like a
soul in pain.

Go thou to an auto-electrics shop and find out what you're drawing
with everything going full blast.  At that point you'll know whether
the alternator is dogging the job or pulling its little heart out --
I suspect the latter.

This is a common problem with ambulances and police cars, by the way.

Yours,
David