1998 Ford Taurus Door locks, interior lite

I own an 98 Taurus. I had this problem developing when the car was three years old. The dealer could not find the solution. I searched extensively the ford boards and the technical bulletins and found the explanation. All door locks has a switch inside to tell the light control module that the door is closed. When that switch is not working properly (is blocked open) the module interprets that the door is ajar and the light stays on. Of course the people try to close the door better to slam it and that works sometimes by dislodging the switch, sometimes the switch remains blocked open. Try this, buy a can of WD-40 insert the straw in the lock (not the key lock but in the triangular opening where is engaging the door post stud) and spray working the lock by opening and closing the door repeatedly. That helped me.