In this image the float arm is horizontal to the mounting flange which means the tank would be full. Here we can sea a near perfect full reading of 33Ω.


If your sending unit reads between 33Ω & 240Ω the sender is working properly and you'll want to investigate the wiring and or the gauge itself.


This is one of the easier tests you can conduct!


NOTE: If you have a European boat or a boat with VDO gauges the resistance readings may be different. Best to check with the gauge manufacturer to see what the input range should be for the sender you are testing.