Rewiring a Hardie RD-900 Without a Diagram

Reconstructing Zone Wiring by Process of Elimination

If you've lost the wiring diagram for your Hardie RD-900 (or any controller), you can rebuild the mapping using a simple field test.

Step-by-Step Rewiring Method

1. Find the common wire: At the valve box, identify the wire connected to all valve solenoids (usually white). Connect this to the controller's C (common) terminal.
2. Test each hot wire: With the controller in manual mode, activate station #1. Touch each remaining field wire to terminal #1 until the corresponding valve opens. Label that wire "Station 1."
3. Repeat for all stations: Move to station #2, #3, etc., matching each wire to its valve.
4. Assign zones logically: Wire stations in the order you want them to run (e.g., front yard, back yard, side).

Tools Needed

• Multimeter (optional, for continuity checks).
• Wire labels or tape and marker.
• Small screwdriver for controller terminals.

Tip

If multiple valves share a common wire, ensure the common is securely connected at the controller and at every valve. A loose common will cause erratic operation.