when testing a sender - plug it onto the harness and turn it upside down, you should hear the float slide to the "top" and the gauge should read full. Then turn it rightside up again, and hear the float slide down, and the gauge should read empty and the low fuel light should
if all that works, push the gauge down into the tank rather quickly, preferably with 3/4 of a tank of fuel or so with a friend watching the gauge. If the gauge rises slowly to 3/4 (5-15 seconds?) then you should be good to go. If it rises instantly then your sender is letting fuel in and out a bit too easily and quickly and the gauge may bounce around when you stop or make a turn. If it rises to 3/4 but it takes more than a minute - then not enough fuel is getting in and out of your sender. You can then reverse the process and lift the sender out again and see how long it takes the needle to drop to zero. This buffering/dampening is designed in to the design of the unit based on the sizes of the holes at the top and bottom of the sender that let fuel and air go in and out of the bottom and top.
On a houston unit (sender only - not sender/pump combo) you can adjust this dampening effect a bit by tightening (to make the needle move slower) or loosening (for faster response) one or both of the phillips screws at the bottom - it doesn't take a lot, try 90 degree adjustments and don't over tighten.
If the needle is not moving, unplug the sender and see if the needle moves at all when you do. It should probably at least twitch. Check for good continuity to ground from the sender harness (black wire?) and check fuse 5.
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then short green black to light green/orange and the low fuel light should come on. If all that works then your wiring is probably okay and the sender is bad.
To check the sender you should see resistance change across black and lg/o as you turn the sender right side and up. And you should find continuity between lg/o and gb when the sender is upright, and no continuity if its upside down.
On oem senders you can check for continuities and voltages at the brass rivets in the top of the sender where the wires are attached.