If it turns out to be transient in Rich’s test, I would suggest doing the same test with the light beginning at the starter (source) end.
Check wire 2 at the Ammeter fuse, if transient there also – check wire 2 at Connector.
Check wire 3 at the Ammeter fuse then at the Connector.
If still haven’t found it you will need to check at the Ammeter itself.