Vehicles having Lucas 11AC alternators were originally fitted with a Lucas 3AW relay that controlled the operation of the dashboard mounted charge lamp.
The second image shows how the relay is connected. Switching the ignition on supplies the warning lamp with 12V, which earths through the 3AW relay, as its contacts are normally closed. As soon as the engine starts, a current from the 'AL' alternator terminal causes the contacts within the 3AW to separate and the warning lamp goes out, showing that the alternator is charging.
Unfortunately, as these mechanical relays are no longer available, our relay (140501) can be used as a replacement on negative earth vehicles.
For positive earth vehicles use relay 140502.
To fit replacement Lucas 3AW relay: