If your fridge freezer is making knocking sounds when it's turned off but still plugged in and running on electricity, there could be a few possible explanations for this issue:
Defrosting cycle: Many modern refrigerators have an automatic defrosting system. During the defrosting cycle, the appliance heats up the cooling coils to melt any accumulated frost or ice. The knocking sound you hear might be caused by the expansion and contraction of the cooling coils or other internal components as they heat up and cool down during the defrosting process.
Compressor noises: The compressor is a crucial component of a fridge freezer, responsible for circulating refrigerant and maintaining the desired temperature. When the fridge is off but still plugged in, the compressor might still occasionally make noise due to internal pressure changes or residual refrigerant movement.
Water flow: Some fridge freezers have water dispensers or ice makers. If there is water left in the lines, it might move or drip, causing a knocking sound.
Uneven surface or leveling: If the fridge freezer is not sitting on a level surface or if it's not properly leveled, it can cause some internal components to rattle or knock against each other when the compressor or other mechanisms are active.
Fan or motor noises: There could be a fan or motor inside the fridge freezer that remains active even when the cooling is off, and these components might generate knocking sounds during their operation.
Internal structure: The internal structure of the fridge freezer, such as shelving or drawers, might not be securely positioned, causing them to knock or rattle against each other when the fridge is powered on.
It's essential to investigate the source of the knocking sounds, as some issues might require professional inspection and repair. If you are unsure about the cause or if the noises are concerning, it's a good idea to contact the manufacturer's customer support or a qualified appliance technician to diagnose and fix the problem.