Error F4 on display, compressor does not start or stops shortly after starting, clicking sound from compressor area

Safety: Unplug the freezer. The compressor area contains live mains components when powered.

• Access compressor compartment: Remove the rear lower service panel to expose the compressor and electrical box.
• Inspect start device: Remove the plastic cover on the compressor terminals. Check the PTC relay and overload protector for burn marks, cracks, or melted plastic.
• Check connections: Ensure all spade connectors are tight on the compressor pins and on the start device.
• Test components: With a multimeter, check continuity of the overload protector and approximate resistance of the PTC relay. Open circuits or obvious damage indicate replacement is needed.
• Replace start device: Install a Bauknecht-compatible compressor start relay/overload kit. Match the model and compressor type.
• Evaluate compressor: If the new start device still results in F4 and repeated clicking, the compressor may be mechanically seized or internally shorted. In that case, a sealed-system repair (compressor replacement) is required and must be done by a certified refrigeration technician.