The 3000 Forum

On my 1967, 3000 Mark III BJ-8. My ignition light came on gradually. I have at least 14 volts, (My volt meter might not be that accurate, but it's more volts than with the engine off.) to the battery with the engine running.

I was told it might be a bad ground, but any ideas where I should start looking?

Tom, Experience has taught me that the first place to go when baffled by electrics, which is the default setting, is, of course, M G Guru. Search M G Guru and drill into the mountains of info to electrics and specifically Ignition Warning Lamp.
Here’s a link:
IGNITION WARNING LAMP - What It Does And Doesn't Do (mgaguru.com)

I find it helps to think of electricity as water. The ignition warning lamp is simply caught in a pressure battle between the generator and the battery. With the generator stationary the battery is pushing water, sorry electricity, back to earth through the generator. When running at faster than idle the pressure is in the opposite direction and, although slightly higher, fairly equal between generator and battery so the lamp doesn't light and the battery gets charged.

To quote the Guru directly:
“What the lamp is doing is monitoring voltage difference between ignition switch (battery voltage) and Dynamo output voltage. When first switched on the lamp sees 12V from ignition switch and no output from the generator. The generator will be "sinking" current to ground through the armature windings. The lamp sees the "D" circuit as a ground connection and lights up brightly.

When engine is running, and the generator is charging properly, the "D" terminal is up around 12-15 volts, a fairly close match to battery voltage (ignition switch output), so very little current flows through the lamp, and the lamp will be dark. When engine is idling slowly the Dynamo output voltage can be significantly lower, say 10-volts perhaps. The lamp then has 12V input from ignition switch and 10V on the other side, which may be enough voltage difference to make the lamp glow dimly (which may be perfectly normal).“
The article goes on to suggest some solutions to problems. Hope this helps. Bill

When we’re the brushes last changed and the generator cleaned internally .

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That’s not an oil leak , it’s my patent pending rust proofing system .

Thanks for all the information about my ignition light!