Simple automotive test rig

I need assistance creating a simple test rig. I do automotive work and had one of these rigs for years but have recently misplaced it. Its used for testing gauges and sending units. It made use of a linear potentiometer, i know that much. In effect, this circuit, by outputting selectable voltages / resistances, mimicked the effect of the float in a fuel tank, allowing for gauge diagnostics. With a 12 volt DC input, two ouptputs were available through the potentiometer and a switch. In one position, the potentiometer would output between 0-100 ohms. In the other position the potentiometer would output 100-1000 ohms. I'm pretty good with automotive electronics, but i did not build the first rig i had, and don't have much experience designing circuits. Any help would be appreciated, (a drawing would be great!).