Temperature Gauge

[Silverback7739]

I really stink at electrical so please be gentle.
I have a 99 Ford Ranger with the 3.0. My temp gauge is pegged out way past the max mark. I replaced the sending unit and the connector with no change. When I move the needle back to the starting point with a magnet it stays until I turn power on then it pegs outagain. I tested the wires and one wire goes directly to ground and the other shows an open circuit.
Where should I start? I can't really afford to take it to a shop right now.

 

[pjtoledo]

the sender itself should read 16 ohms hot, 275 ohms cold.
the open wire should have voltage on it.

my book is for a 2000, probably should wait for someone with a 1999 wiring book to comment as there may be differences.

 

[Silverback7739]

The open wire should have voltage when the key is turned on or always?

 

[pjtoledo]

I would assume key on.