Troubleshooting Irrigation Solenoids

Posted by John Hamilton

Troubleshooting Irrigation Solenoids is the first step in the electrical troubleshooting process. In this article we will look at a step by step approach on how to quickly identify if you have a bad solenoid which is not operating correctly. *We are not addressing power (Volt's) output problems from the Satellite and will assume that the voltage output is functioning correctly.

Step 1 - Check Hydraulics

Ensure hydraulics are working correctly before any electrical troubleshooting! Manually operate the valve and ensure that the selector switch is in the 'Auto' position. Check to make sure that all shut off and isolation valves are open.

Step 2 - Ohm's resistance test (Test a 'New Solenoid' off the shelf)

Take a new solenoid off the shelf and read what the Ohm's resistance of a new solenoid is. Most irrigation solenoids will read approximately 29 ohm's of resistance; yet, may vary depending on manufacturer. Reading a new solenoid will give you a baseline on what you should see in the field before taking field readings with your Voltmeter.

Step 3 - Check Ohm's Resistance at the SATELLITE

Troubleshooting Irrigation Solenoids*Before digging (nobody gets excited about this), it is always easiest to check the Ohm's resistance of the circuit from the Satellite.

A) Disconnect the 'Common Wire' (White) from Terminal Strip in the Satellite.

B) Measure the Ohm's resistance of the circuit by touching your Volt Meter leads across the circuit. The resistance reading on your voltmeter may read slightly higher than your baseline reading of the Solenoid from the shelf (29 ohm's). The length of wire will add resistance to the wire circuit and increase the resistance reading of your meter reading.

If you are reading above 50 ohm's or higher (single solenoid circuit), this could be an indicator that the solenoid is going bad. If the reading is below 20 ohm's, it could also be an indicator that the solenoid is failing.

*Note! Readings may be higher or lower if multiple Solenoids are wired together in Series or Parallel circuits.

If you are reading an open circuit (0, or 0.L), it could indicate that you either have a burned out Solenoid, or a cut field wire. *For more details on Voltmeter readings, read your manual!

Step 4 - Check Solenoid Resistance (Ohms's) at the VALVE

Solenoid Resistance TestA) Disconnect the field Solenoid at the valve from the Wire Circuit before testing.

B) Look for burned wires. (Very common and may be an indicator of a burnt Solenoid)

C) Inspect the wire connections (DBY's) to ensure that there was not a bad splice in the field

D) Look for any charred or burning on the Solenoid itself (This is an indicator that the solenoid is burned and the coil within no longer works)

E) Disconnect the Solenoid from the circuit by cutting the Wire Splice's off (ensure you have plenty of wire left to reconnect).

F) Measure the Ohms Resistance of the Solenoid with your Voltmeter as described in Step 3.
If Solenoid reads either 0, or L.0, replace the Solenoid with a new one.

G) If Solenoid reads with the appropriate range of 20-50 ohms, your problem may lie in the wire path itself and more advanced wire troubleshooting techniques will be required.