Control panel displays E05 and heating is disabled

Safety first: Unplug the spa before loosening any fittings. Running the heater without water can permanently damage it.

• Verify water level: Fill the spa so that the water is at or slightly above the maximum line recommended by Bestway.
• Clean/replace filter: Remove the filter cartridge and clean it thoroughly. Try running the spa briefly without the filter to see if E05 clears (do not use the spa long-term without a filter).
• Bleed air from heater:
  • With power disconnected, slightly loosen the upper hose connection at the pump/heater until air escapes and water begins to flow.
  • Retighten the connection securely.
• Check for leaks: Inspect around the heater housing and hose connections for signs of water loss that could expose the heater.

If E05 continues after restoring proper water level and flow, the internal flow switch or pressure sensor may be defective and the heater assembly may need professional service or replacement.