If I remember right Kerry is on to something. The Valve is given voltage between 0 and 12. The more voltage it gets the more it opens. So as you adjust your temp wheel, the valve opens and closes. I will recheck this afternoon because I was eventually going to rig past the ccu and control it independently along with another variable control for the fan

__________________
1983 W123 300D Turbo
2000 F250 7.3 Powerstroke