Troubleshooting Irrigation System Electrical Problems

When something goes wrong with an irrigation system the cause is not always obvious. Sometimes the problem is electrical, such as when a zone won’t turn on, or no zones will run. 

There are three areas to check when investigating the electrical part of the system: the controller, the field wiring, and the electric solenoid valves. However, most of the time the problem isn’t the solenoid.

Controller Troubleshooting

Everything is initiated from the controller, so this is the first place to start. But first, check the obvious: 

• Is the water turned on and is there power to the pump?
• Are isolation and master valves open all the way?
• Is the controller set to the rain/off function, or is the rain sensor preventing the system from turning on?
• Has the controller been programmed properly?

No Zones Working

Basic electrical troubleshooting steps to take if no zones will run:

1. Is the power source working?

• You might have a blank screen, or if there’s a display, the power may be coming from the battery. Verify the controller is plugged in. Press the reset button if plugged into a GFCI (ground fault circuit interrupter) outlet.
• Use a test lamp or any other 110VAC device to determine if there’s voltage at the outlet.
• For hard-wired controllers, check the circuit breaker at the main breaker box. Warning: only a licensed electrician or irrigation contractor should test hard-wired transformers.

2. Is the transformer working?

• Use a multimeter on the AC voltage setting to check the transformer’s output either on the two transformer wires or at the two AC screw terminals on the controller — the reading should be between 24 and 28 volts. Replace if the reading is outside the acceptable range.

3. Is the display scrambled, or the controller isn’t responding to input?

• Sometimes a power surge causes it to lockup. Reset the microprocessor by disconnecting the power and any battery backup for up to 10 minutes. You can also use the reset button. Then reconnect the power and reprogram.

4. Is the fuse burned out or is there a bad fuse? 

• Replace it.

5. Are all the wires properly attached to the terminal strip?

• Tighten any loose wires.

If the zones still won’t turn on, repair or replace the controller.

Some Zones are Working

If some of the zones aren’t working, follow these basic electrical troubleshooting steps using a multimeter:

1. Verify the controller is programmed correctly.
2. Set the multimeter to the AC voltage setting to check that the controller is outputting the correct voltage to the non-working stations:

• Manually start the controller and turn on the non-working zone.
• Place the black probe on the common terminal and the red probe on the terminal for the non-working zone.
• The controller should be sending out a signal in the 24-28 volt range.
• Repeat this for any other zones that won’t turn on. If the voltage output for a station is lower than the recommendation in the owner’s manual, but is above 0, the controller is defective.

3. If the controller is outputting the proper voltage for the non-working zones, then check the continuity of the circuit (resistance or ohms). This will help you identify a wiring problem between the controller and the sprinkler valve that prevents the valve from opening:

• Turn off the controller. Never check resistance through a live circuit.
• Set the multimeter to the ohms setting (Ω or ~).
• Undo the common wire from the controller.
• Place the multimeter’s black probe on the end of the common wire, and the red probe on the wire of an unworking station. You should get a reading between 20 and 60 ohms.

4. Readings from ohm testing indicate the following:

• Less than 20 — a short circuit caused by a damaged solenoid with a short inside, two valve wires touching directly or touching through soil or water.
• More than 60 (in the hundreds) — a partial connection caused by a bad splice (corroded, or incomplete contact), or partially broken wire.
• OL or 1 — open circuit caused by a broken wire, a disconnected splice, a disconnected wire from a terminal or other connection, or a malfunctioning solenoid. Check your multimeter’s manual for the symbol used for an open wire. It could also be an infinity symbol (∞), or numbers followed by an “m” or “k” (e.g. 1.1m or 28k).

5. Exceptions to the ohm readings:

• The ohm reading of two solenoids connected to a single station will be almost half that of a single solenoid. Check each solenoid separately in this case.
• Stations with several solenoids will have proportionately lower resistance readings.
• Rain Bird has a solenoid valve where the normal range is 70-85 ohms.

Solenoid Valve Electrical Troubleshooting

1. Next go to the solenoid valve or valves with controller ohm readings outside the normal range:

• See if you can immediately spot something wrong (e.g. bare wires touching, station wire and valve wire separated, cut or nicked wire, splice corroded or separated) and do the repair.

2. After the repair, go back to the controller and test the resistance again to see if it’s within range. If not, return to the solenoid and continue with the following steps:

• Disconnect the solenoid from the field wires (do this as the first step if no obvious repairs needed during initial inspection). Test the resistance by touching the multimeter probes to both solenoid wires. If the solenoid measures below 20 ohms here as well as at the controller, then you must replace the solenoid because it has shorted out. Remember to check each solenoid if more than one is connected to a single station.
• If the reading at the solenoid is good, the short is in the field wiring between the controller and valve. Fault locators are available for finding short circuits and cut wires in the field.

3. If the reading for the solenoid is still above 60 ohms, but not “open”, look for a bad splice.
4. For an “open” solenoid reading, replace the solenoid. If the reading is good compared to the controller’s, then there’s a wiring problem between the controller and valve. A wire and valve locater will help you find broken and cut wires in the field.
5. You can also check voltage at the zone valve. At the controller run the zone you’re testing, then:

•  At the valve, set the multimeter to the AC voltage setting and connect to the common and station wire. Look for a similar reading you got at the controller (24-28 volts). If there’s proper voltage at the valve, then the problem is the valve, but if the multimeter shows zero, 1, or OL, the problem is the wiring.

South Austin Irrigation are the experts in irrigation system troubleshooting and repair.  Call us at (512) 534-7449 or contact us online to keep your sprinkler system operating at peak performance.