Bike Light Not Working Due to Dynamo Power Generation Failure

The dynamo hub or bottle generator is failing to produce the required alternating current (AC) output, typically 6V and 3W, despite the wheel spinning at an adequate speed. This diagnostic indicates that the issue is internal to the generator mechanism rather than the external electrical circuit. Common signs include a lack of voltage output when tested with a multimeter at the dynamo terminals, or physical symptoms such as internal 'play' or grinding noises within the hub assembly, which suggest the internal magnet assembly has become loose or misaligned. If the dynamo fails to generate power even when isolated from the rest of the lighting system, the internal components of the generator are likely compromised.