Intermittent Valve Error on Zone 5: Solenoid or Wiring Fault?

After Controller Swap, Zone 5 Error Returns; Manual Valve Works

If a valve operates when manually opened at the valve box but fails via the controller, the solenoid is likely failing under load (heat) or the field wiring has a high‑resistance short.

Steps

1. Replace the solenoid on zone 5 (most common fix).
2. If the error persists, inspect the field wires for nicks, corrosion, or splices touching ground.
3. Test the controller’s output voltage at the zone 5 terminal while the error is active—should be 24 VAC.

Nine times out of ten, a new solenoid resolves the issue.