Rain Bird ESP Modular Controller "4 Err": Zone 4 Short Circuit Diagnosis

Error Meaning

"4 Err" indicates a short circuit on Zone 4. The controller's internal breaker trips to prevent damage. The alarm light may stay on from a prior rain sensor event.

Step-by-Step Isolation

1. Clear error: Set dial to AUTO, press ADVANCE.
2. Disconnect Zone 4 valve wires at the solenoid (both wires, keep separated).
3. Manually run Zone 4 from controller.
4. Observe: - Error returns → short in field wiring between controller and valve. - No error → solenoid is shorted; replace it.

Why This Works

Removing the solenoid isolates the valve from the circuit. If the controller still sees a short, the fault is in the wires (nicked, crossed, water in splice). If the short disappears, the solenoid coil is internally shorted — a common failure.

Next Steps

• For wiring fault: inspect splice boxes, rodent damage, shovel cuts. Repair or replace wire run.
• For bad solenoid: unscrew old, install new (same brand/model). Reconnect wires, test.