89 fuel tank sending unit wires ?

[turbocamino]

  Gentlemen, The 3 wires coming out of the sending unit and into a plug on the right side are green with red trace , solid green and black,, I found the black to be a good ground.  The green/red lights a test light but very dim,key on not running, and the solid green shows nothing with the test light.I've grounded both those and the gauge needle doesn't budge.I think i read that the green/red is the "low Fuel" light?  Not sure about my next move,,any suggestions appreciated.

[turbocamino]

I forgot to mention that the gauge is inop and am attempting to diagnose this issue...