bottom of gauge as there is room above full line for bobber to go which would mean if top of bobber is above full line than your tank is more than full
check for a damaged fuel tank
The most common cause for a malfunctioning fuel gauge its the sending unit. It is located in the top of the fuel tank and the tank must be removed to replace it.
A common problem with a gas gauge is the sending unit. The sending unit is located inside of the fuel tank and is removed through an access on the top of the tank.
If it takes 30.00 to top off the gas tank, but the gas gauge shows full on an 85 F150 4.9 Straight 6, it is likely that the gauge is not reading correctly. Replacing the gauge cable can remedy this.
sending unit bad on top of fuel tank
the oil pressure sensor, for a dash with idiot lights (no gauge), is located on the top of the engine at the back behind the distributor virtically screwed in. The oil guage sensor, for a dash with an oil gauge, is located above the oil filter on the drivers side of the engine screwed in horizontally.
its located in the tank. you need to drop the tank in order to get to it as it comes out from the top.
you can unhook the wires to the sender on top of the tank and with a 12v test light - find the terminal that blinks on and off and ground it -with the key on - and the gauge should go to full if gauge is functioning ----if not it may be a bad gauge
wire of the unit on top of gas tank or fuse blown
the tank on a grand caravan is like a town and country like i had you have to take the straps loose on the tank , and drop the tank down about a foot the sensor is on top of tank near the gauge
id say either a bad ground to chassis on the fuel sending unit (off the top of the tank.) or a bad gauge
Most likely inside the fuel tank. You will have to drop the fuel tank and remove the retaining ring on top of the tank and the pump/gauge/filter assembly will come out.