Pump controller displays E04 and the pump will not start; sometimes occurs intermittently.

Safety: Turn off power at the breaker before opening any electrical enclosures.

• Remove extension leads: Onga pool pumps should be wired directly to a dedicated circuit, not via long, undersized extension cords. Connect directly to the fixed pool pump outlet.
• Check plug and outlet: Inspect for heat damage, discoloration, or looseness. Replace any burnt outlets or plugs.
• Inspect wiring connections: In the pump terminal box, ensure active, neutral, and earth connections are tight and not corroded. Tighten terminal screws.
• Bypass external controls: Temporarily bypass external timers or automation relays (if safe and competent) to see if E04 clears. A failing contactor or timer can cause voltage drop.
• Measure voltage: If you have the skills and tools, measure voltage at the pump while attempting to start. If it drops significantly below the motor rating, consult an electrician.

Persistent E04 indicates a supply or controller issue that should be addressed by a licensed electrician or pool technician.