This project uses the W1209 thermostat board. What I did was make a few small modification to the board:

1. remove the 20k smd resistor next to the sensor connector,
2. throw the sensor in the junk box,
3. add a 10k resistor across the sensor connector (underneath if a smd resistor or remove the connector if using a through hole resistor)
4. add a 30k resistor (or two 15k resistors in series) from the upper terminal of the sensor connector to the +12v rail.

Then I built a 1A constant current load from a 5v regulator and two 10 ohm resistors. You probably have those in your junk box ready for a project like this.

My binary used the sensor port as part of the serial communications so I had to remove the surface mount cap. Later binaries which you will use now interface the serial communications via the + and - keys. Full marks to the project team for that.