I'm planning to use the fuel level warning light on my dash but I need to know what resistance from the sensor it triggers at.

Does anybody know? Or do I need to put a variable resistor in and experiment?

Then I can work out what size resistor I'll need in the circuit to make it work with my sensor unit and come on at a sensible level.

Also need to know the resistance range of a Racetch sender unit as I don't want to take mine out to see and can't be arsed filling/emptying to find out either!

Adrian