Date:         Fri, 5 Jul 2013 20:30:20 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Fridge- last problem before our trip.
Comments: To: Jeremy Stovin <jjstov@yahoo.com>
In-Reply-To:  <BE06D1D0-64CE-4825-BB50-19C3FDE36797@yahoo.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 07:55 PM 7/5/2013, Jeremy Stovin wrote:
>I believe the led is measuring the aux battery. Not 100% sure. I
>know the aux battery powers the fridge.  When I got the van, there
>was some creative wiring, and then I added a Yandina. See link to
>rough drawing I did last year.
>
>I will try to check the voltages. I know all the other stuff
>connected to the aux, such as interior lights, 12v outlets, and
>radio, all work.
>
>
>http://images.thesamba.com/vw/gallery/pix/952132.jpg

Ok, according to the diagram both kitchen and fridge run direct from
the house battery with no relay control of the fridge.  The LED panel
runs off the kitchen circuit so it's measuring the house battery.

The LED panel is supposed to be calibrated so the green light turns
yellow below 12.5 V, and red below either 12.0 or 11.5, I forget
which.  The absolute magnitude is adjustable by a pot on the board,
but the intervals are not.

The three lights are an attempt to give some vague idea of battery
state of charge, but it's to some extent doomed because the battery
voltage varies depending on load.  The execution is also flawed
because the monitoring circuit ground goes to the fridge DC power
ground and is affected by the voltage drop along the wire between
there and where it goes to the chassis behind the fridge.

So if the light turns yellow when you drop the fridge load on it
*without* the motor running, I wouldn't find that too surprising,
though a poor ground behind the fridge wouldn't help.  If the light
turns yellow while the house battery is being charged by the engine,
that would suggest a poor ground to me.  If your drawing is accurate
the panel is taking its positive measurement point direct from the
house battery terminal, so wiring losses on the supply side shouldn't
enter in, unless you've got a poor connection from house battery post
to its terminal.

Yrs,
d