the light should come on the dash,then go out once its started. if it doesnt come on at all, and youve replaced the batt and alt then it must be a fault with the wiring to it all. check the blue wire hasnt come undone near the battery on the +terminal, and if thats fine check continuity of all the associated wires,the big one from batt to starter to alt, then the small blue signal wire from alt to batt connection, then to your clocks