At 10:14 PM 8/6/2010 Friday, Ed Wiebe wrote:
>http://picasaweb.google.ca/ewieber/WestyDomesticWaterTankLevelSensor#
>you can see the broken part.  What is it and is it easy to find a
>working replacement.  It shouldn't be hard to solder a new part in.

It's a reed switch.  *If* it has only two leads, any one you can find
should work.  I have a nasty feeling, though, that it's the kind with
three, which is harder to find.  If so, you need to be looking for an
SPDT reed switch.  I can't quite tell from the pictures and it's been
too many years since I've been inside one of these things.   If it's
a three-lead one and only two leads are used, you need the pair that
are normally closed. While you're installing it, resolder the other
one so there's some slack in the leads -- that's why it broke in the
first place, the twinkies didn't give it any room to stretch if the
rod gets bent a little.  When you put it back together, make sure
it's absolutely watertight, because a couple drops of water inside
will make it misbehave.  The weakest point for sealing is where the
wire comes out the top.

>By the way, can someone explain how the unit senses the water level?

Yes.  How much detail do you want?  Basically, the float has a magnet
in it, and when the magnet gets near the little reed switches they
switch.  That throws the resistors in and out of the circuit,
changing the voltage.

Yours,
David