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Clicking Solenoid After Replacement: Controller or Wiring Fault

A solenoid that clicks repeatedly (plunger chattering) after replacement indicates inconsistent current from the controller or a wiring issue—not a bad solenoid. The plunger needs steady 24 VAC to hold open; pulsed voltage causes chatter.

Diagnostic Test: Isolate Controller vs. Field

Disconnect all field wires at controller terminal strip.
Connect new solenoid directly to controller: one lead to C (common), one to zone 1 terminal.
Manually activate zone 1.
If clicking persists: Controller output is faulty (pulsed/unstable voltage). Replace controller.
If smooth operation: Field wiring has high resistance, corrosion, or partial short. Inspect all splices.

Why Chattering Happens

Controller output transistor failing (thermal damage)
Corroded wire splices adding resistance
Multiple solenoids on one zone drawing excess current
Wire run too long for gauge (voltage drop)

Don't Replace All Solenoids Yet

The clicking is an electrical symptom. Replacing diaphragms won't fix it. Test the controller output first with a known-good solenoid. If controller is bad, a modern Hunter XC or Rain Bird ESP-TM2 is a reliable, affordable replacement.

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