as the title states, my fuel sender needs replacing because it shows empty all the time except when the tank is full it shows a full reading and it will show the reading just over 3/4's full but as soon as it drops any lower (about 130 km's distance after filling tank up) the fuel gauge will drop slowly all the way until it finally shows below empty and stays there for the next 500 kms or so, maybe more depending on what type of driving I'm doing (highway, city/stop-start, etc.)
The strange thing is the fuel light will then illuminate, indicating that the fuel level is very low. Don't get me wrong...i like that the "low fuel warning" lamp illuminates, telling me that I need to get my ass to a servo before the car dies. But I'm just wondering if anyone knows why or how the fuel sender can know the fuel level is low, and not display it on the gauge.
If anyone can shed light by explaining it here, i would greatly appreciate it.
Thanks guys,
Anth.

The fuel light is triggered by a separate switch in the fuel gauge float assembly. The gauge not working would probably be due to either some crud on the resistor bank in the gauge sensor, or the resistor bank being worn through. When there is no connection, the gauge goes to zero. Pull the senor out and examine it. Clean it or replace it.

The fuel light is triggered by a separate switch in the fuel gauge float assembly. The gauge not working would probably be due to either some crud on the resistor bank in the gauge sensor, or the resistor bank being worn through. When there is no connection, the gauge goes to zero. Pull the senor out and examine it. Clean it or replace it.

cheers, yeah i've already done that (removed sender/examined/cleaned/sanded with 1200grit wet) still doing the same thing. i even used 2 different contact cleaners with strong alkaline content but still nothing. it has shit itself and i know it needs replacing but i was wondering what exactly triggers the low fuel light. it cant be the float or circuit board as it always shows empty. unless when the float does reach the bottom and that part of the circuit board still works, triggering the light to illuminate.
thanks for your input mate

Usually on the same bracket there is a small cylindrical device that has a NTC thermistor in it.
As long as its dunked in petrol it stays cool, otherwise, its resistance drops and begins to power a series connected light bulb in the dash.
Not sure why you would want to rely on a device heating up in a fuel tank, but thats how they work.

Have you polished the wiper contact to remove any varnish builds up on that?

yep polished the wiper contact as well. its gone so i'll just replace the sender with a new one. they selling em on ebay (genuine mits part) for around $142 or something in that range anyway.
i dont mind spending $ on the TF exec its a good car and it has been really reliable and drives fantastic. it also hauls on the highway...it revs hard and is real smooth and stable at speeds up to 180 km/h i had it to. new tyres, new bushes all round, new shocks and engine mounts really does make a difference in ride quality.
anyway, cheers for your input