H21 error, compressor runs briefly then stops, freezer warms

Safety: Unplug the freezer. The compressor and inverter operate at dangerous voltages.

Steps:

• 1. Ventilation check: Ensure the condenser coil at the rear or bottom is clean and that there is adequate space around the unit. Clean dust from the condenser with a soft brush or vacuum.
• 2. Compressor temperature: After the unit has been off for 30 minutes, touch the compressor shell carefully. Extremely high temperature may indicate overload or mechanical failure.
• 3. Wiring and overload: Inspect the compressor overload protector and wiring harness for signs of burning or loose connections. Reseat connectors.
• 4. Listen to startup: Restore power and listen: a brief hum followed by a click and H21 suggests a locked rotor or inverter fault.
• 5. Advanced checks: A technician can measure compressor current and inverter output waveforms. If the compressor windings test normal but H21 persists, the inverter PCB is suspect. If windings are out of spec or shorted, the compressor must be replaced.

Note: Compressor or inverter replacement is complex and requires refrigerant handling certification; contact a Panasonic-authorized service center.