Safety: Unplug the freezer. The defrost heater operates at mains voltage and is near sharp metal fins.

Steps:

1. Access evaporator: Remove baskets and inner rear panel to expose the evaporator coil, defrost heater, and thermal fuse.
2. Visual inspection: Look for burnt spots on the heater, melted insulation, or a blown thermal fuse (often wrapped and clipped to the evaporator tubing).
3. Continuity test: Disconnect the heater leads and measure resistance. An open circuit indicates a failed heater. Do the same for the thermal fuse; it should read closed.
4. Wiring check: Inspect the harness from the heater and fuse back to the cabinet connector for breaks or corrosion.
5. Replace failed components: Install the correct Panasonic defrost heater and/or thermal fuse kit. Secure them in the original positions and avoid contact with plastic parts.
6. Control relay: If heater and fuse are good, the defrost relay on the main control PCB may be faulty, requiring board replacement.

H23 displayed, freezer temperature unstable, may overcool or undercool

Possible Causes