I just replaced the sender unit on our fuel tank
this weekend. I have analog gauges. If you also have analog gauges, make sure you have power to the gauge, the wires leading to your sender unit have good conductivity, then check that the sender unit, if analog, reads and varies the resistance ( 33-240 Ohms).
I used this
sender unit to replace my old defective analog sender.
I also am adding sending units to my water tanks
. The water tanks
have a visual gauge on the tank. To view the water level, you need to lift
the mattress, climb over and site the gauge through a little hole in the wood bunk frame. That is the case for both tanks. Not easy, so its not done as we should. Gauge on the dash would be most helpful.