Low voltage in battery, all the time

[Brett Dikeman]

At 8:29 AM -0800 1/9/04, pasquale pilato wrote:

>Victim is a 1990 100q.  I have had this problem for a
>little while now, when I go to start my car, there is
>very little voltage (<8v).  Lights are very dim, and
>there is not enough voltage to crank the engine.  When
>I hook up an auxiliary battery (been driving without a
>back seat for weeks) and start the car, the car starts
>fine, and when it is running, I have almost 14v on the
>dash voltmeter.  Some more info, when Iím driving, and
>the lights are on, and the stereo cranked, the dash
>voltmeter drops to a hair above 12v. (have a 1 farad
>capacitor to install) The yellow battery light in the
>middle of the tach and speedometer never goes on.
>What I donít know is if the battery canít hold a
>charge, it is new and still under Sears warranty.  Or
>if the alternator is not making enough charge, or if I
>have a leak in the air compressor system, and that
>thing runs all the time draining the battery.

Air compressor system?  You mean the locking system pump under the back seat?

In any case- you need to do a few things.  First, hook up a lamp(or 
an ammeter) in SERIES with either the ground or positive cable.  If 
the bulb lights and everything is turned off(inc interior lights and 
footwell lights, you'll have to wait a bit), pull a fuse, see if it 
goes out, put fuse back.  Work your way down the line until you find 
the culprit.

If it doesn't light, or you see draw around 100ma or so(that's normal 
range), then it's time to look at the battery.  See:

http://uuhome.de/william.darden/carfaq4.htm

If the battery is OK, you need to have the alternator checked out, 
but measure resistance from various points in the + cable(ie between 
battery and alternator post for example) to see if you have the 
infamous cable splice problem.

Brett
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