Hardie RD-600 Valves Click but Won't Open – Wiring or Voltage Issue

Symptoms: Clicking Solenoids, No Water Flow

After replacing all four valves on a Hardie RD-600 system, the two front zones work, but the two rear zones only produce a clicking sound from the solenoids. Water flows only when the manual bleed screw is opened. New solenoids and a controller reset didn't help.

Check Controller Output Voltage

Measure AC voltage between the COM terminal and each zone terminal at the controller while that zone is active. You should see 23–27 VAC. If voltage is low or absent, the controller or its wiring is at fault.

Field Wiring Inspection

If controller voltage is correct, the problem lies in the field wiring to the rear valves. A tiny nick in the wire insulation can create a high-resistance short that prevents the solenoid from pulling in fully, causing the click without opening. Recent digging in the yard is a common cause.

Troubleshooting Steps

1. Verify 24 VAC at the controller terminals for zones 3 and 4.
2. If voltage is good, disconnect the field wires at the valve box and measure resistance to ground; a short to ground will show low resistance.
3. Trace and repair any damaged wire. Consider running new wire if the damage is extensive.

Once the wiring is sound, the valves should open normally.