Fuel tank switch/valve problems

[dwjack]

This fall I replaced the passenger fuel tank and ever since the fuel gauge reads way past full but only for that tank. I made sure that the sending unit ground was good, it was so I figured the problem was inside the sending unit and planned on replacing it. Since then I have been using the driver side tank.

Tonight I went out to my truck and the gauge went way past full on the driver tank. I switched it to pass. back to driver but the gauge stayed there and it didn't sound normal when switching them. I could hear it running but not as long as normal.

I read that the valve isn't supposed to have power for the pass. tank. If the switch was bad would it automatically default to that tank?