Display shows F7; ice buildup may be excessive, or defrost cycles may not complete properly.

Safety first: Unplug the appliance. The defrost heater operates at mains voltage; do not test it live unless you are qualified.

Step-by-step:

• Access evaporator and heater: Remove freezer drawers and the rear inner panel to expose the evaporator and heater assembly (often a metal tube or wire element attached to the coil).
• Visual inspection: Look for burnt spots, broken heater sections, or disconnected wires.
• Continuity test: Disconnect the heater leads and measure resistance with a multimeter. An open circuit indicates a failed heater or thermal fuse.
• Check thermal fuse (if separate): Some Liebherr models use an inline thermal fuse or safety thermostat. Test for continuity and replace if open.
• Replace heater assembly: Install a new Liebherr defrost heater (and thermal fuse if integrated). Route wires as originally and secure with clips.
• Reassemble and test: Refit panels, restore power, and monitor for proper defrosting over several days. The F7 code should clear once a successful defrost cycle completes.