Hello Eric,
Good news. It was a failing DOPA! Replaced and it works, SPAN pot and ZERO pot works. Except that the last 2 LEDs won't turn off and the upper 2 LEDs won't light.
#1 Measuring the voltages on vo1, it reads (from full tank to empty) 0.63v to 3.1v and beyond but I can't get below 0.63v. Note that I can go beyond 3.1v (Since I'm using a 200 Ohm trimpot to emulate the sender) but not below 0.63v (0 resistance already).
#2 Measuring the voltages on vo2, it reads (from full tank to empty) 2.40v to 0.64v but I can't get below 0.64v. Note that I can't get past 0.64v even if I increase resistance since I'm using a 200 Ohm trimpot to emulate the sender and I can only get 2.40v at an empty tank (at 10 Ohms-Empty and even at 0 Ohms it is only 2.41v).
The above measurements were taken at the standard SPAN and ZERO pot settings (14.5K and 19K). Increasing the ZERO pot's resistance will light the 2 upper LEDs (Making it an 8 functioning LEDs), but can't get to turn off the 2 lower LEDs even by tweaking both trim pots.
As a result, Only 6 LEDs are functioning on the full fuel sender range. The last 2 LEDs stays on forever, while the upper 2 leds don't light forever the (0.64v to 2.40v range) at the standard pot settings.
Any ways to fix these? I think were on the finalizing part already.
Edit: Measuring VS, I can also get 0.07v to 0.77v and beyond (200 Ohm pot) from Full to empty tank.