Originally Posted by debugger
Not true. The accuracy depends entirely on the geometrics of the tank. At full up ( either arm/float or ring, the sender will be at 30 ohms. At full down, the sender will be at 230 ohms. At halfway it will be at 130 ohms. At halfway, the actual display will say half but there may be more or less fuel depending on the bottom position of the float relative to the actual tank bottom, the geometry of the tank and the angle of the tank.
If the tank in question is full or close to full of fuel and the battery supply to the gauge is intermittent, the gauge will read full or empty depending on the battery connection. If the battery connection is loose and the sender is at half position, the gauge will read half or empth depending on the battery connection,
If the sender/tank ground is loose, the guage will read either empty or the level of the fuel. Same thing if the lead between the gauge and the sender is intermittent. These conditions apply to gauges that respond rapidly to level changes. These are the electromechanical type. There are some thermal types of gauge mechanisms and they act differently and slower to input changes.
The sender could be bad but we don't have solid evidence yet. If I knew what the estimated fuel level is, I may be able to eliminate some possibilities. In other words if the tank is relatively empty ( or half empty), it is unlikely that the gauge would swing between full and empty. Regardles, you still wouldn't know if the problem is the sender or the gauge without testing.