My 1999 F150 did not have the switch down on the bottom of the doors, mine was located up by the handle that opens the rear doors. I lubricated and manuvered them to see if the were sticking but to no avail. Saturday I again, trying to see if I could fix it had negitive results. I then started cleaning the interior when I noticed that the corners of both rear doors were bent outwords approximately 3/4 of an inch and had gone through the rubber. I then bent them back in and the door ajar light went out and stayed out.

Hope this helps anyone else.

 

Corners bent out? Which corners?

 

The upper left hand side corners. The ones that if the drivers door is closed first you can see were the back door would hit the front.