hi Bucktruck, which truck and gauge exactly, i don't know for sure if they all work the same way, on my 1950 truck, the gauge will go down to empty (below empty) when the power is off, the needle will slowly bottom out with gravity, if you remove the mechanism from the truck and flip it, or flip the whole truck onto the roof in a ditch, you will see the needle will fall to full position when power is removed the needle has NO spring, it is pulled to marking state between two electro magnets, and when those magnets lose power the needle should fall slowely I attached a photo showing my needle at bottomed out position
if your needle stays at full, maybe it's just sticking a bit? -s
