Onga controller shows E09 and pump stops unexpectedly during normal filtration.

Safety: Isolate power before disassembling any hydraulic components.

• Observe pump while running: If the pump basket is not full of water and you see swirling air, the pump is losing prime.
• Check for blockages: Inspect skimmer, pump basket, and any suction cleaner lines for obstructions. Remove debris.
• Inspect flexible hoses: On above-ground pools with Onga pumps, check for kinks or collapsed hoses on the suction side. Replace soft or flattened hoses.
• Filter maintenance: Backwash the Onga sand filter or clean the cartridge to reduce restriction and prevent cavitation.
• Re-prime: Fill the pump housing with water and restart. Monitor for stable, air-free operation.

If E09 recurs, a suction-side leak or underground pipe issue is likely and should be investigated by a pool technician.