Here is the guide I received from WEMA Kus, in 2022 when my fresh water tank sensor completely deteriorated. It was when WEMA stopped farming out their manufacturing to lesser quality suppliers.
If your sensor seems to be working now this is an excellent check method. Very straight forward and simple.
Boat Sending Unit
use this method, it comes from WEMA Gauges.
To test the sender simply:
- Disconnect the two wires on top of the sender.
- Remove the sender from the tank.
- Connect the wires on the sender to a multimeter.
- Set the multimeter to resistance [Ω ohms]
- Move the float to the top of the sender and take a reading on the multimeter:
- At the top of the sender (full) the resistance should be:
- European specification - 190 ohms
- American specification - 30 ohms
- Move the float to the bottom of the sender and take a second reading:
- At the bottom of the sender (empty) the resistance should be:
- European specification - 0 ohms
- American specification - 240 ohms
If you don't get the expected resistance reading on the multimeter then the sender is at fault and will need replacing.