I just bought a second-hand bike for my daughter knowing that the dynamo hub was not working and now I would like to try and repair it. I tested that the dynamo does not produce electricity.
I also verified that the positive contact wire is always in short-circuit with the hub body, both before and after disassembling the hub. That to me means there's something seriously wrong inside the dynamo and I will need to replace it, at least the internal magnet. I am just not 100% sure with these new (to me) hubs.
Can anyone confirm that there should NOT be any contact between the wire and the internal assembly ?
Edit: this is a Shimano DH-3N20 Dynhub. There's only one cable coming out of the assembly. I used a multimeter on the cable and on the shaft. I suspect the previous owner attempted some clumsy repairs, perhaps damaging the cable.