As mentioned in a previous post my Door Ajar Light (and hence Dome light) was coming on and off the past couple months after WD40 would not work anymore. I bought a new switch (about $19, see link below) and replaced it. It took about 3 hours because I spent quite a bit of time inspecting how the switch was mounted inside the door frame with one of my wifes compact makeup mirrors. Here's are the replacement steps I recommend.

1) Remove door panel.
2) Remove the 2 plastic screws which are holding the bottom back corner of the foam sheet and fold the foam sheet back to get access to the large hole in the door frame.
3) There is a vertical bracket iknside the foor that is bolted near the bottom of the door. Though I could not remove the bracket after removing the bottom bolt I was able to move it enough to get better access.
4) Unplug the wire from the Electric Lock plug and the Door Switch plug.
5) Remove the 3 external Torque bolts holding the latching assembly. This will allow you reach in through the frame access hole and manuver the assembly a couple inches without disconnecting all the linkage to it.
6) The door switch is mounted in a locking bracket and has to be turned clockwise about 120 degrees to disengage the tooth shaped locktab on the switch (see pic).
7) Install new switch and reassemble.
8) Reassemble door panel

F250 Door Ajar Switch picture by dcara - Photobucket

If you don't want to replace the switch you can just unplug it inside the door frame to disable the dashboard and dome light.

 

Good writeup. You make it sound easy. It isn't that hard but just kind of hard to get to.

 

That's great thanks. I got to number 5 a few weeks ago and couldn't get the dang thing out. Didn't know which way to turn or how far and was ascared I would break something. I did manage to break a lock tab of the harness connector but it still works with one.

 

I can't believe it!! After working great for a few days it has now started doing the same thing it used to do. The door ajar light is staying on again and the dome light comes on and off as I drive down the road. I guess I'll try unplugging the switch and make sure that stops the problem. If it does then there must be something loose in the door latch mechanism itself that is activating the switch.

 

Hi...I found those switches to be crap. A dry connector in the door panel! We went thru 3 in each door! Lotsa miles later...with no dome light...good luck.