Technical Generator light does not turn off

[F30Msport]

Recently the generator light had decided to stay lit, no matter the conditions. A few months ago I replaced the coil and points as well as rebuilt the starter, not that those should affect the light...

How can I diagnose this issue? The car runs perfect, but the light is driving me mad.

 

[bugsymike]

Recently the generator light had decided to stay lit, no matter the conditions. A few months ago I replaced the coil and points as well as rebuilt the starter, not that those should affect the light...

How can I diagnose this issue? The car runs perfect, but the light is driving me mad.

Generally you should be experiencing a flat battery by now, due to worn brushes etc. in dynamo.
Here is a simple circuit to give an idea of where feed should at warning light on a dynamo system with negative earth. Assuming not a later alternator set up.

 

[F30Msport]

Thanks, but forgive my ignorance when it comes to electrical circuitry. Any guidance on troubleshooting this is appreciated.

 

[bugsymike]

Firstly do you know the generator is working, if you haven't got a meter try putting the headlights on shining against a wall , then start the car and rev up, the lights should come up brighter.
If they do then it suggests that the dynamo is working OK , but that you have a wiring fault , so possibly check any wires you may have disturbed when working on vehicle, or if you fitted a radio or spotlights etc.

 

[F30Msport]

The lights don't change at all when I rev the engine. So I guess I need to rebuild the Dynamo?

 

[The Panda Nut]

I agree with Bugsymike and would say yes almost certainly this is what you must do. Worn brushes and / or commutator likely the cause. Dont leave it or you will end up stranded with a flat battery. Do check the wires on your generator are properly attached first though.

 

[bugsymike]

I agree with Bugsymike and would say yes almost certainly this is what you must do. Worn brushes and / or commutator likely the cause. Dont leave it or you will end up stranded with a flat battery. Do check the wires on your generator are properly attached first though.

Yes, if lucky it may be just a case of cleaning the commutator and fitting a set of brushes, something quite common in the old days.
However if you have not done it before, it may be an idea to read up about it, as it is important that the commutator segments are clean with no muck between sections which will cause it to short across. Also the brushes do need to be fitted correctly concerning the electrical connection and the spring tension allowing smooth good contact between brushes and commutator.
After having done it once it soon becomes fairly straight forward and easy, but the same as with any job it does need doing correctly.