Why does my blender make a rattling or buzzing noise?

A rattling or buzzing noise can come from loose assembly, trapped ingredients, a hard object in the jar or a motor that is under strain. If the noise is sudden, loud or accompanied by smell, stop using the blender straight away.

1. Switch off and unplug the blender. Expected result: the appliance should be safe to inspect without movement.
2. Check the jar, lid and blade unit for anything loose. Expected result: all parts should fit snugly and not shake when handled gently.
3. Look inside the jar for hard items such as ice chunks, seeds, pips or packaging pieces. Expected result: only suitable ingredients should remain. Remove anything that should not be blended.
4. Restart with a smaller amount and a lower load. Expected result: the noise should become steadier and less harsh if the jar was overfilled.
5. Inspect the blades for bending, chips or rubbing against the jar base. Expected result: the blades should turn freely and evenly.

Stop using the blender if the noise continues with an empty jar, if the base vibrates strongly or if any component appears damaged. If the fault remains unresolved, contact the retailer or store where it was purchased. The Tristar BL-4431 uses stainless steel blades and a lockable safety switch, so a secure fit and suitable ingredients are important for normal operation.