After my front wheel got damaged I took it to the BS where I purchased it and they replaced it.

However, after riding it I have noticed that with the new wheel the dynamo hub (Shimano Nexus) works intermittently, probably because of problems with the connections between the wiring and the dynamo.

I have tried bringing it back to the shop for a check, but of course while there the dynamo was working fine and the light was doing its work, so the guy could not find anything wrong with it, just to have it dark again once I was close to home.

Before going again to the shop, I would like to check it by myself: I suspect it is either the wires going into the plug to be loose-ish or the connection between the plug and the case in the dynamo to be shaky.

Is there any check I can do to eventually fix it?

  • I've given a generic answer, but knowing the make and model of the hub and lights, and whether it's a 2-wire or 1-wire+frame connection would help narrow things down
    – Chris H
    Feb 19, 2023 at 8:20
  • @ChrisH, added info on the dynamo
    – L.Dutch
    Feb 19, 2023 at 16:23

1 Answer 1


It's most likely to be the connection in the plug. These are pretty simple and often rely on just stripping the wires and using the plastic plug shell to hold them in place. So you can pull off the plug (as you would for removing the wheel), clean the contacts on the hub, and have a look at the bars end of the wires. You may want to cut them off and strip fresh wire. On some hubs, with some wire, it's best to strip about twice the length of the contact and fold the wire over to double the thickness. Other combinations won't go together if you do that.

If your hub uses a return connection through the frame, check and clean all contacts in that path, such as the light mount.

Connections within the hub are not generally meant to be user serviceable, and will depend heavily on the exact hub.

  • Exactly. Leaves only the question, why we are still tolerating such beep connections in our safety critical hardware?!? Feb 19, 2023 at 22:57
  • @cmaster-reinstatemonica with both of mine, if it works immediately after putting the wheel on, it keeps working, and unlike a proper plug, if you take the wheel off without undoing it first, in any likely orientation, it doesn't break anything, just disconnects. Where I have had failures is elsewhere in the system, cables chafing for example, or lights not working after filling with water
    – Chris H
    Feb 20, 2023 at 6:37

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