Ignition warning lamp wiring question

[kartman24]

Hope someone can help me with a wiring question, i am just finishing rewiring my 1960 kit car with a new loom, there are two wires for the ignition warning lamp, a brown/yellow from the alternator and a white live from the ignition. I have bought one of those plastic generic dashboard warning lamps, this has two pins on the back which has got me confused, these type of lamps usually work with a live feed and an earth wire, will this operate for my application by just using the two loom wires with no earth to the lamp? There is no original loom with this car to use as a guide.
Many thanks for any advice............Martin

[TwinKam]

It's correct.
With the ignition on, engine not running, the lamp gets +12v on one side from the ignition switch, and an earth through the (static) alternator on the other, so the bulb lights up.
With the engine running and the alternator now charging, the bulb still gets that +12v from the ignition switch but now also gets +12v from the alternator, so the bulb doesn't light up.

Edited by TwinKam on Friday 24th March 20:58

[kartman24]

Many thanks for that, your description of how it works is great, i didn`t realise the brown/yellow earthed through the alternator when the engine is not running. The loom supplier technical guy was scratching his head over this question!

[TwinKam]

kartman24 said:

Many thanks for that, your description of how it works is great, i didn`t realise the brown/yellow earthed through the alternator when the engine is not running. The loom supplier technical guy was scratching his head over this question!

EFA