Alternator Light

Take a meter and verify one side of the bulb is getting 12 VDC and the other side is wired to L on the regulator.

Thanks for your advice. I'll try this.

You can see the diagram of the operation of the "L" terminal (either with a lamp or with a led)
To check and test the regulator's "L" terminal, first measure that the regulator's ground is properly connected to the negative pole of the battery. The mass of the regulator must be "faultless"
Also check all the terminals of the regulator connector, this connector has often caused many problems ...
switch off all avionics which could consume excessively current, due to a fault
If the LED or lamp remains On with the engine running above 2000 RPM, stop the engine and disconnect the "L" terminal
Then place an Ohmeter between terminal "L" and the regulator earth. if you measure a very low resistance (see zero) the Mosfet transistor of the regulator is dead ... And it is not repairable other than by changing the regulator ...
You can do a final check:
disconnect the old wiring from the "L" terminal.
Connect a lamp or a led (with its resistance) as on the diagram, directly on the positive terminal of the battery and on the terminal "L", without connecting anything on the negative terminal of the battery.
(One wire on the positive of the battery and the other on the terminal "L", with the lamp or the led in between)
The lamp or led should light up
Start the engine and test at 2000 rpm (or more), the lamp or the LED should go out.
Take this opportunity to measure the charging voltage, which must be greater than 12V (approximately 13V5 - 13V8 depending on the state of the battery)
If the test works well, test lamp off when the engine is running, check the wiring of your charge light, or even better, change it.
Beware of a lamp holder that can touch the ground of the plane, because poorly insulated.
One last thing useful for all, when you find the fault, tell us what it was!

Jacques, appreciate your thorough reply, thank you.

I will follow your instructions and be certain to post my findings within a week.

Thanks again.

Here are my findings about the alternator light not illuminating with ignition.

The previous owner had 2 red lights fitted. One labelled Alternator and the other labelled Starter Engaged Light.

Once I began testing the circuit, it became clear to me that he has labelled the lights incorrectly!!

The starter light is actually the alternator light and vice versa.

So basically the lights have never worked in the correct manner.

How strange!!

I've now swapped the labels.

Thanks again for your advice.