Oso water heater shows E17; heating is disabled until the fault clears.

Safety first: This fault can indicate a shock hazard. Do not operate the heater until the cause is found. Isolate power and, if in doubt, contact a qualified electrician.

• Visual inspection: With power off, remove covers and look for signs of water ingress, burned insulation, or wires contacting sharp metal edges.
• Test element to earth: Disconnect the element wires and measure resistance from each terminal to the metal flange/body. Any measurable continuity indicates a ground fault; replace the element.
• Check cable clamps: Ensure incoming and internal cables are properly clamped and not pinched.
• Dry out moisture: If condensation or leaks are present, fix the leak source, dry the compartment thoroughly, and then retest.
• RCD check: If an external RCD is tripping, have an electrician test it for proper operation.