Technical Fuel water contamination switch

[Brucepeter2007]

1999 1.9Td - water in fuel light came on. Opened drain at bottom of fuel filter and drained out but dash light stayed on. (Always worked before). Disconnected the electric sender plug at the bottom of the filter and dash light went off but after reconnecting the dash light came on again…
Does anyone know where a new water in fuel sender unit can be purchased.
Picture just for general layout
Any help gratefully received

 

[Brucepeter2007]

As an update for anyone in the future as I had no replies - there is a switching transistor built into the fuel sender that is encapsulated in plastic and unrepairable. The transistor base is switched by the lesser resistance from the water which then illuminates the water in fuel warning light on your dash display…
The sensors are all the same but have different screw thread sizes which is a shame as a sensor for a Saab was less than £10 but the part for my Fiat comes in at £50+
As it stands I’m going to disconnect it and just drain it every now and again…
Hope this helps others in future.