Do I have a bad fuel sending unit?

[64stpside]

Now that I got my truck running right tonight, I decided to take on my fuel gauge issue. I put a new gas tank and sending unit in. I didn't put much gas in after I installed everything. I thought all was good because the gauge went to 1/4 tank. I put 5 more gallons in this week because I was going to try to take another test drive. Well, the gauge didn't move. If I remove the ground at the sending unit, the gauge pegs to full, with it connected it stays at 1/4. When the key is off, the needle drops....slowly. I took the sending unit out and moved the float and the gauge still says at 1/4. Did I get a bad sending unit or is the power wire grounding between the gauge and sending unit? I did see a post about the resistor on the gauge being a possible culprit. I decided to turn the key forward and reach up under the dash and start wiggling wires to set if that changed any thing, it didn't but when I touched the resistor on the back of the gauge, it was hot. I got a mirror to check the resistor and it's still intact but I'm not sure how to check it.