There are two types of level sensors, an electro-mechanical "float type"
that I only know about form hearing about it on this list (I think it's in
later Westies), and a multi-point exposed contact system (which is what I
have in my '85 Westie).

I've never stuck a probe in the water, but this system definitely uses the
water as a "conductor" to determine the level.

At 08:56 AM 9/19/2005 -0700, Michael Elliott wrote:
>I've not seen a writeup about how the water tank level sensing systems
>work (there were two types, I think). I don't know if  they have exposed
>+12vdc points in the water. Fresh water is a darn good insulator. But
>the more dissolved solids, such as minerals i.e., hard water,  in the
>water, the greater the conductivity. The combination of a very high
>impedance voltmeter (such as a good digital voltmeter) and hard water
>might very well result in enough current flow to register on the meter.
>
>--
>
>Mike "Rocket J Squirrel" Elliott
>71 Type 2: the Wonderbus
>84 Westfalia: Mellow Yellow ("The Electrical Banana")
>KG6RCR
>
>
>
>On 9/19/2005 8:20 AM Robert Harris wrote:
>
>>hi y'all,
>>Yesterday I was trying to diagnose a dead sink water pump, and in the
>>process happened to discover that the water in my Westy holding tank
>>always
>>has a voltage of +0.3 volts, even when all systems are
>>off.  Ummmmm!!!!!????  Is this normal?  I am wondering if the water level
>>LED "meter" thingy is malfunctioning.  No schematic handy.  The meter
>>does
>>work fine and turning it on makes the voltage of the water go up to
>>+1.5volts.  This is an '84 Westy.
>>
>>In the interest of science if anybody could stick a multimeter probe in
>>their water tank and see if there's voltage when everything's off, I'd be
>>grateful.
>>
>>thanks,
>>Robert H
>>Ithaca, NY
>>84 Westy "Busaru"