RD‑900: Three Stations Work Intermittently – Circuit Board or Wiring Fault?

Three stations on an RD‑900 fail to run automatically or manually, though they occasionally work. Panel and battery replaced, wires wiggled.

Diagnosis

1. Use a multimeter: activate a dead zone, measure voltage at the controller between common and that zone’s terminal.
2. If voltage is 22‑26 VAC, the field wiring or valve solenoid is at fault.
3. If voltage is low/missing, the controller’s circuit board or panel is defective.

Check common wire connections at the valves first; if good, the panel likely needs replacement.