This from another thread in the 12vdc category:
The switch labeled "Aisle" next to the step light switch must be in the off position for this feature to work. Additionally, it is triggered by the entrance door not the screen door.
The two brass plungers at the bottom of the door are for the key-less entry, not the welcome back light. Early models had a black plunger while current models have an internal magnetic switch that operates this feature.
The light is triggered when the entrance door is opened and will remain lit for approximately 1 minute and then dim out. If the door is left open, it will not work again until the door is closed.
Because it works by breaking ground circuit, the light will come back on if the door is not closed before it dims out the next time the door closes. If the aisle light switch is left on, it overrides the circuitry and the light simply remains lit until it is manually switched off.