fuel gauge problem

I have a montana 2001, got problem with fuel gauge it was flactuating around, changed just sennding sensor now after refueling it goes to full and after a while drops to zero, checked the undeneath plug box it's clean and when I unplug it gauge drops to zero, how could I find out what's cause the problem, what's the resistor reading of sending sensor on empty and full? and how I can measure it?

I believe that you should read about 40 ohms when the tank is empty. Another way to test the wiring, is to connect a pot to the wiring and slowly turn the pot and see what the fuel gauge is doing. The ohm reading I believe it is 200 ohms. I would use a 250 ohm pot to test the wiring and the gauge.

Thanks for reply, I am gonna check it, I suspect the mechanic didn't change sending sensor right or maybe the problem is fuel floater in the tank.....