Question
I have a RD900 with 7 active zones.  Zones 3,5,6 stopped working.  I don't even here the water coming on at the water heater like I normally do when I turn on a zone.  This happened about a year ago also and before I looked into getting it fixed, they started working again a week later when I tried to turn them on one last time.  I don't even know what I am looking at with the wiring behind the dial, so I would not know whether anything there is messed up or not.  Any suggestions ?

Answer
Hey Jeff, I hope this helps. I would think, since 3 valves either work at the same time, or don't work at the same time, it is either a bad common wire connection, either at the controller, or at the valves. In the back of the controller, you will see a terminal marked C (for common). Just make sure these wires have a good connection, (tighten down the terminal screw). Also at the valves, make sure that where the wires are hooked to the solenoids, that you also have a good connection. The common wire runs to all the valves, so if you have a bad common wire connection at one of the valves, the continuity might not be getting to the rest of the valves. Just check all your wire connections at the controller, and at all the valve solenoids. Good luck and let me know if you need anymore assistance. Thanks and have a great day.