Dynamo and LED. For posterity

[abowie]

There is a thread of mine on battery charging failure in my 3.8.

viewtopic.php?f=3&t=22046

For posterity I eventually found that the problem was caused by my using a LED globe on the alternator light on the dash.

The alternator light connection feeds power to the field coil in the dynamo. With the LED which is a diode not enough power was getting to the field coils and so they wouldn’t energise.

I replaced the dynamo with a Dynamator. It also failed to charge when the car was started although would sometimes start working after maybe 5 minutes.

The Dynamator needs a minimum 2.8W incandescent globe to power the field coils.

Hopefully this saves someone else from the very frustrating time I’ve had trying to nut this out.

[Tommd]

Andrew, FWIW, the LED should have had nothing to do with the original generator system not working. The indicator bulb in that system does not feed the fields or in any other way effect the charging, it is merely an indicator between two wires.
It also surprises me on the new alternator in generator disguise, that once the alternator did start charging that sometimes it would then stop. Typically, the LED circuit is no longer needed to continue to charge as most modern alternators feed the rotor internally once initially charging. But I do not know enough about that system to be able to say for sure.
Tom