Dawie wrote: ↑Mon May 31, 2021 10:16 am If feed to ign coil is indirect... (As via relay, ecu, etc).
This can happen. There is a tiny current via alt light which keeps relay or electronic switch energized. Normally if switched ign power directly feeds coil, this small current is inadequate to continue sparking.
Try a diode in series with blue wire to alternator. Marking on diode should face towards alternator side.
Correct, the feed to ecu is via relay.
Will give it a go. Will a 1N5821 also do the trick ? I do have them in the garage.
Thanks Dawie.