2002 FORD WINDSTAR.BATTERY LIGHT COMES ON AFTER 5 SEC IDLING, CHANGED ALTERNATOR, BATTERY AND ECU?

2002 FORD WINDSTAR.BATTERY LIGHT COMES ON AFTER 5 SEC IDLING, CHANGED ALTERNATOR, BATTERY AND ECU?

You changed all of that without testing if the cables, connections and wiring were good?

Go to a proper mechanic and have them look at it. If they are good, they'll perform a voltage drop test on both sides of the circuit before condemning any parts.