I get many calls a month from contractors trying to trouble-shoot electric irrigation valves. There are many reasons that can keep a valve from operating properly. The most common problem and easiest to identify is electrical issues. If you own and know how to use a volt-ohm meter.
You can test the 24 volt electrical wiring and solenoids of an irrigation system with a volt-ohm meter at the irrigation controller.
First, you need a simple digital volt-ohm meter, $10 to $20 unit range will work just fine. Set the dial or switch to the ohms setting. The icon will be the Omega symbol that looks like a horseshoe. You can test your meter by touching the leads together and watching the display go close to zero. The meter is sending out an electrical current and measuring the resistance (electrical “pressure” loss) thru the wiring.
Second, you must disconnect the wire or wires from the common post of the irrigation controller. This wire is called the common wire, it is connected to each of the electric valves in the field.
Now take one of the volt-ohm meter leads and hold it on the disconnected common wire. Take the other meter lead and hold it to the valve station wire on the controller terminal block that is malfunctioning. Make note of the resistance reading on the meter.
A normal functioning circuit reading would be 20 to 60 ohms of resistance. You can confirm this by taking reading from other valve circuits that you know work.
If your meter display doesn’t change when you touch the valve wiring, I sorry to inform you that you have a cut wire in the circuit.
If your meter display is between 1 to 15 ohms of resistance, you have a short in the circuit. A short reading will usually indicate a damaged solenoid.
If your meter display is between 60 to 110 ohms of resistance, you have a bad electrical splice in the circuit. This will more than likely be the splice at the electric valve.
The ohm readings will only help you identify the nature of the electrical problem. This will eliminate the trial and error method of trouble-shooting. You must now find the cut wires, bad solenoids and poor splices. Good Luck

Jay Hughes, CID
Branch Manager
Simmons Irrigation Supply
Charlotte, North Carolina