need adjustable voltage trip relay

I need some help from you guys! I'm working on a project that requires an adjustable voltage trip relay. This will be used to control the electric lockers in a Ram Power Wagon. What I have is a knob with 3 positions. In position 1, I've got 0.9V on the output wire. Position 2 I've got 1.9V, and Position 3 I've got 2.7V. I purchased the product below from ACI but I misread the description and it requires 24V and will not work on a 12V system. I landed all of my wiring and adjusted the pots and the LED's for each relay function perfectly, but there's not enough voltage there to trip the relays. What else can I do? I don't need anything that will handle a lot of current since all I am doing is triggering a separate 30/40A relay for each axle's locker. http://workaci.com/products/aar-analog-input-2-adjustable-relay-outputs

Use a comparator. Typical single supply comparators are cheap ($1?) and available in quad packages. (eg - LM339 from memory.) There are plenty of tutorials and circuit examples in webland.

Jameco Electronics has a 12 to 24 Converter for $22.95. Might be a simple / inexpensive way to make what you've already done work. http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_175813_-1