Fuel gauge questions

[Jimbo Billy Bob]

I have noticed a few threads mention that their fuel gauge is reading at half when the tank is actually full. I have a 68 RoadRunner that does the same thing with a new sending unit. I am about to replace the sending unit again and was wondering if I am really on the right track. Could it be the resistor on the back of the gauge panel??? The other instrument gauges and lights work fine so I'm a little confused. Thanks for you input in advance.

 

[hunt2elk]

Unhook the wire from the back of the fuel gauge. Check the resistance from this wire to ground with a known amount of gas in the tank. The readings roughly should be 73 ohms = empty, 34 ohms = half, 10 ohms = full. If you don't have something close to this then your gauge may need to be calibrated, or bend your float arm on the sending unit. The voltage limiter drops the voltage to 5 volts to the fuel and temp gauge and doesn't affect these readings unless it is shorted or burned open.

 

[Jimbo Billy Bob]

Thanks hunt2elk, soundsl like you know your stuff. This gives me a great path to go down. Thanks for your help