Heater shows H18; may be associated with circulation or internal pump issues on models with built‑in pump.

Electrical and burn hazard: Turn OFF power and allow the unit to cool before working on the pump or internal piping.

• 1. Listen for pump operation: When the unit starts, you should hear a low humming from the pump. If silent or noisy, suspect a pump issue.
• 2. Bleed air (if model supports):
  • Follow the Panasonic manual to open any bleed valves and remove trapped air from the internal circuit.
• 3. Inspect pump (qualified persons):
  • Remove the front cover.
  • Locate the circulation pump on the water circuit.
  • Check wiring and connector for secure fit.
• 4. Free a stuck impeller:
  • Some pumps have a service screw to manually turn the shaft. Gently rotate to free a stuck impeller.
• 5. If H18 persists: Replace the circulation pump assembly with a Panasonic‑approved part. This may require draining the unit and should be done by a technician.