Hyundai Repair: Fuel gauge not reading properly, hyundai santa fe, gas gauge

Question
I have a 2003 Hyundai Santa Fe.  My gas gauge does not read properly.  I have run out of gas 2x.  It has been in for service 4 times for the same problem (no one seems to know what it is).  When I fill my tank up the needle on the fuel gauge starts to go up and then goes down to empty and my gas light comes on.  This will go on for days and then eventually the needle will begin to move up towards the full mark. What do you think the problem could be and how many times do I have to take it in for service before something can be done.  

Answer
This sounds like the fuel sender is not working properly an maybe there could be a wireing problem from the sender to the sender any one that knows how to read a volt matter can find this problem,so make sure there have ase testing one there techs lol.go to the deal an ask how there CSI is an ask to see the rateing this way you know if they can do what you need.