Dishwasher shows H04 and stops, often early in the cycle

Safety first: Disconnect power at the breaker. Heating components operate at mains voltage and can cause electric shock.

• Confirm symptom: Run a short cycle and check if the water and door interior remain cold throughout. Hazy or poorly dried dishes also indicate no heating.
• Access heater: Remove the lower front panel and, if necessary, pull the dishwasher out. Panasonic dishwashers typically use an inline flow-through heater on the circulation pump assembly or a base-mounted heater.
• Inspect wiring: Check heater terminals and wiring harness for signs of burning, discoloration, or loose connectors. Reseat any loose plugs.
• Test heater resistance: With a multimeter set to ohms and power disconnected, measure resistance across the heater terminals. A typical reading is between 20–40 Ω. An open circuit (infinite resistance) indicates a failed heater.
• Check NTC sensor: Locate the NTC temperature sensor (often clipped into the sump or heater housing). Measure its resistance at room temperature and compare with Panasonic specifications; a short or open reading indicates failure.

If the heater and NTC test good, the main control PCB heater relay may be defective. Board-level repair is complex and should be handled by a technician.