It is of great importance for the dynamos ability to "start", that the commutator, and spaces between the commutator panels are clean. The commutator can be cleaned with a piece of fine grained sandpaper, and the spaces with a broken junior saw blade or similar that fits in with.

Please note that the commutator is round, an oval commutator slings the brushes off at higher speeds (voltage drops at higher revs).

On systems with electronic regulator, it is normal that the charging lamp glows faintly, this is due to a small loss over the diode that acts as charging relay.

Starting help. After a longer stand still, the dynamo sometimes have " starting troubles".

On B type dynamos (Lucas etc), connect D to F briefly, and perhaps to the battery, with the engine running at low revs. Keep all lights turned off.

On A type (Bosch) dynamos, connect F to chassis briefly, and perhaps D to battery, with engine running at low revs. Again, keep all lights turned off.