image by Seemann: morguefile.com
Irrigation sprinkler systems control the flow of water with the help of electronic valves. The system works by using a time clock that sends a 12-volt signal to the valve at a designated time the owner of the system sets. An electronically actuated solenoid on the valve receives the signal through two wires that connect the clock and the valve. The 12-volt signal instructs the solenoid to open the normally closed valve and allows water to flow. The process is simple; however, several mechanical parts must work in unison for the system to work properly. If one goes array, the whole system fails.
Check all the easy and obvious things first. Did someone unplug the clock? Did a circuit breaker trip in the garage causing a loss of power, or did a fuse blow in the clock? How about the water supply; did someone shut it off for some reason?
Check your irrigation clock owners' manual to locate the fuse for your brand of clock.
If the irrigation clock has power, and the main water supply valve is in the open position (right to close, left to open), try to use the clock to open and close the electronic valves manually. All irrigation clocks can operate in the manual position. They do differ however, in the method in which they allow you to operate them manually. Find your instruction manual for your brand of clock to perform this step.
Each irrigation system will have more than one valve. If you were able to get any of them to work in the last step, you know that the irrigation timer is properly sending out the 12-volt signal. If none of them will work, locate the electronic valves. Find them in a valve box buried in the yard. Inside the valve-box, locate the two wires leading to the top of each valve. The device that the wires attach to is the valve's solenoid. Grasp the solenoid and turn it ¼ to ½ turn to the left. Water should begin to flow as you turn the solenoid; if not, double check the main water supply to verify the water is on to the system.
If you are able to turn the water on in step 3, the problem is electrical. Check the wire connections in the valve box that connect the valve to the clock. Remove the wire nut connecting the wires, and clean the connection with electrical wire cleaner. Re-connect the wires with the wire nut, and, using the clock, attempt to operate the valves manually once again.
If the valve is still not working, check to determine if the solenoid is functioning properly. Use a volt-ohm meter to check the resistance of the solenoid. Each meter operates slightly different; follow the instructions for yours to complete this task. According to Rain Bird, a solenoid is functioning properly if "resistance is between 20 and 60 ohms."
If the solenoid is bad, replace it by unscrewing the old one and screwing in a new one. Purchase them direct from the valve manufacturer or your local home improvement store.
If you are still having problems or do not have access to a volt-ohm meter, it is time to call a landscape professional to give you a hand with locating the problem.