I have a model 3 with a 912 UL, 13 gal tank in right wing, 6 gal tank in left wing and an aluminum header tank behind the seat that is vented to the top of the right wing tank. I fly with the right tank on service and the left tank isolated.

I have experienced the deafening silence when fuel level gets low and the outlet gets unported.

I would like to install a low fuel warning in the header tank vent line, but I am concerned that I will get a lot of spurious alarms.

I have been watching the fuel level in the vent line, and I would assume that the level should be equal to the right tank level, but it never is. I normally see a level that is a couple inches lower that the bottom of the wing tank.

Could the wing tank being pressurized cause this indication, and if I install the low fuel warning switch in the header tank vent line, will it operate correctly?

thanks

Louie