The Toptron panel drives one analogue needle for battery and tanks, and none of it is documented. The new panel reads the same signal the old gauge did, through the same 86 Ω load, and shows volts and percent on the original dial’s scales — plus weather and a clock.
Why
Every assumption had to be measured: the output only exists while a selector is held, it’s a current drive rather than a voltage, and its ground floats 0.3 V above the battery’s. Bench-verified and tested live in the dash; the final install is next.