In an irrigation system where each head can be run independent of others, each head has its own control wires and solenoid. The process of changing this solenoid is very similar to changing the solenoid on a control valve. The major difference is the need to make sure that the entire system has no water pressure. If the system has pressure, then when the solenoid is removed, the person changing the solenoid will get wet.
Turn off the water supply for the system. Some systems have valves that can turn off certain areas without turning off the entire system.
Turn on five heads around the one with the bad solenoid to release pressure from the system. When the heads stop running, the system is ready.
Dig around the bad head until the solenoid and wires are exposed. The solenoid on most heads is located directly under the manual control switch on the head. Make sure to expose about one foot of the irrigation wires.
Cut the irrigation wires at the direct bury connectors for the solenoid. This will help to ensure a proper connection with the new solenoid.
Twist the old solenoid loose from the irrigation head.
Twist the new solenoid in place. Make sure the threads are clean before installing the new solenoid.
Strip the irrigation wires to expose half an inch of copper. Then connect them to the solenoid with the direct bury connector. Make sure to cap the connections with the supplied wire nuts and push the wire nut all the way to the bottom of the grease tube before closing.
Turn the water supply back on and make sure the head runs by the controller. Fill the hole back in around the head.