Andy,

First check the wire connections between the controller and the problem zone's solenoid. See if the wire at the controller or at the valve has come loose. If you are not familiar with a controller/solenoid connection, then google information on how it works. It is unusual to be stuck open so also turn the solenoid itself clockwise and see if you can turn off the problem zone and then back on again. The easiest solution is to replace the solenoid and see if that works. To see if it is the controller switch wires for that zone with another solenoid valve and see if the problem shifts to the new zone, then replace the controller. If it is not the solenoid or the controller replace the valve. Do one thing at a time to isolate the cause. Just like working on a car problem. Aloha