i have a lennox lch803 3 stage chiller with an expansion valve fault. when the plant goes into a start up procedure it pre heats the valves(danfoss tq 55) as normal then goes into valve fail. i have 0-10v from control panel driving the vop relay panel and a 24v feed pre- heating the valve. the sensor cable is also in tact and have been continuity tested. any ideas????