Triumph Repair: Spitfire fuel cage calibration, wound resistor, tank unit

Question
Is there a way to calibrate the fuel cage to read correctily.  Does the gauge have a screw on the back or what?  It seems that my gauge reads about 1/4 tank off.

Answer
Hi Michael,
If there is an adjustment I have not seen it. If it is that far off, something is wrong not out of adjustment. You didn't tell me what year Spitfire.

Most have a voltage stabilizer that powers the gauge at 10v which can fail. Other possible problems are, the tank unit is a wire wound resistor and you need to operate the float and watch to see if it's arm is bent and check to see that the correct voltage is applied to the voltage stabilizer as a problem with the charging system can make the reading wrong or even a bad engine to frame ground problem.
Howard