Date: Fri, 7 Jan 2000 16:11:20 -0500
Reply-To: David Beierl <dbeierl@IBM.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@IBM.NET>
Subject: Re: What about us?: H2O tank senders solved!
In-Reply-To: <01BF5923.FF975B20@ip98.raleigh13.nc.pub-ip.psi.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 15:29 1/7/00 , Bulley wrote:
>What about the poor sods like me who have the older, "solid state" sensor
>set up, with the three probes up the side of the tank? Does anyone know
>what breaks/fixes these?
Oh, all right... <g>
The LED panels were designed for the original electrode system, so nothing
changes there.
The water-level circuit supplies 12v through a 1 megohm resistor to the
green wire going to the sender, and reads the resulting voltage on the
green wire. It is set up to light the green LED from 0-3 volts (full),
yellow from 3-5 (almost full to getting low), red from 5-7 (getting low),
and no light at all above 7 volts (about a quart left -- the wand-type
senders do not provide the no-lights indication).
The green wire goes to a little magic box mounted on the wall of the
"secret" compartment, and thence to the electrodes in the tank.
Bulley, you have no lights at all -- if you put some water in the tank,
then measure from ground to the green wire with a high-impedance meter (10
megohms or greater) and see less than 7 volts, your panel is
busted. Chances are it's bad solder (reflow the joints) or the LM324 chip
on the left side, and if you are up to PC soldering work you can replace it
with one from Radio Shack (p/n 276-1711) for $1.29.
OTOH if you see over 7 volts with water in the tank, there's a problem with
your sender or the wiring to it, or maybe you're using triple-distilled
water in the tank. Check for continuity to the little black widget and to
the electrodes. If you have it, easiest thing would be try another black
widget. Might also put half a teaspoon of salt in the tank and see if that
makes a difference, also make sure the electrodes aren't crudded up
(unlikely). If necessary I can measure out my widget. It's potted, so you
can't see the innards directly.
This electrode setup is a bit flakey since it depends on the conductivity
of water in the tank. On mine I had to fudge one of the resistors on the
LED panel to keep the red light from giving a false indication. Go to
http://pws.prserv.net/synergy/Vanagon/ and pick LED panel, then look at the
water circuit schematic.
david
david
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
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