How to Troubleshoot Your Irrigation System by Measuring Resistance

Introduction

To work with the Yardian Pro, a compatible system (including wiring, splice, and the solenoid coil) should have a resistance reading between 26 ohm (due to the 1A current limitation) and 200 ohm. Please also make sure the irrigation wiring and the wire splices are well sealed so that they won't be exposed to soil and moisture.

How to Measure

This picture shows how a valve is connected to a zone on the Yardian Pro controller. Simply use a multimeter to measure point 1 and point 2 in the picture with the wires removed from the terminals, which will let you know the overall resistance (including the wiring, the wire splice, and the solenoid coil). You can also measure point 5 and point 6 to get the resistance of the coil to further identify the root cause.

Resistance Reading

A reading that’s too low may be caused by: 

• Valve wires touching together
• Valve wires connected through soil or water
• A damaged solenoid that’s been shorted inside

A reading that’s too high may be caused by:

• Corroded splices
• Partially broken wires
• Wires aren’t making actual contact