Why does the door lights up on the dash and keeps dinging?

I am having the same problem with my 1998 Windstar. I have not fixed it yet, but have read that you should try spraying WD40 on all of the contact points, on all of the doors. From what I read thus far, it may take a day for this to make any effect on the car. Also, it is not a permanent fix to the problem, but can definatly help that annoying * ding*ding*ding* for a little while at least. Hope this helps, I am going to try it when I go home tonight, so i will let you know if it worked on monday.