Pump controller displays E04 and the motor will not start; sometimes occurs after lightning or surges.

Safety: Isolate power and wait several minutes for internal capacitors in the inverter to discharge before opening any covers.

• Check supply voltage: Measure the incoming mains voltage and ensure it is within the range specified for the Certikin variable speed pump or controller.
• Inspect for surge damage: Look for burn marks, bulging capacitors, or a burnt smell inside the inverter/control module. If present, the unit must be replaced.
• Review deceleration settings: If the pump is connected to an external control system, ensure it is not commanding very rapid stop/start cycles that can cause DC bus overvoltage.
• Reset the controller: Follow the Certikin manual to clear E04 (usually power cycle plus RESET). If the error returns immediately, the inverter is likely defective.

Due to the high voltages involved, replacement of the inverter or control module should be carried out by a qualified technician.