The bulb powers the alternator by initiating the charge process, connect the thick wires to the alt and battery, then it should be ok, unless the alt is buggered, just touch a LIVE onto the IND terminal whilst engine is running, and this will start the charging process if ok, it would certainly appear to be as it is getting live through the bulb and earth from the alt(this IND changes to LIVE when outputting)
tabetha