David Beierl is your man for this. He knows more about the tank water level system(s) than even the designers :-)

The later version with the long stick and floating donut is a reed switch based system I think. Magnet in donut, reed switches in stick.

But David is your man. Most likely he has mailed a reply already.

Alistair

> On Oct 3, 2016, at 3:45 PM, Neil2 <vidublu@GMAIL.COM> wrote:
> 
> I posted an inquiry awhile back but everyone musta been on holiday.  My '90
> sensor always shows 100% on the LEDs and I'm wondering how the sensor
> actually works.  The float seems too light to use an electric device.
> 
> Please advise if you've ever had this symptom and the model van and sensor
> type to ensure I don't chase my tail on this.  Thanks!
> 
> --
> Neil2
> '82 Diesel Westfalia (Ducky)
> '86 Vanagon (SaVannah)
> '08 170" 2500 Mega Roof Sprinter (Moby)
> '90 Westfalia Subagon
> Fulltiming since August 2008
> Nunquam Pendite Divendium