I have a Hunter PRO-C that has worked for years. Now it shows that stations are watering but, no water is coming out of the heads. If I manually actuate the valves they work so, I know it's got water. For whatever reason, the controler isn't sending the signal to open the valves. I have tried re-setting the whole system and reprogramed the PRO-C. I have also by-passed the rain sensor. Any ideas as to why it's not working?