Oso water heater shows E18; may be associated with frequent on/off cycling or unstable readings.

Safety first: Isolate power before adjusting sensor wiring.

• Secure sensor: Ensure the NTC sensor is firmly seated in its pocket and cannot move or rattle.
• Reroute wiring: Keep sensor cables away from high‑voltage or high‑current conductors to reduce interference.
• Check cable integrity: Replace any sensor cable with damaged insulation or shielding.
• Ferrite or filtering: If recommended by Oso, fit ferrite beads or filters to the sensor leads to reduce noise.