What are the more obscure issues with the door ajar light!

If you have replaced the door switch and it is now functioning correctly, but the door ajar light is still coming on when you close the door, there may be an issue with the door latch or a wiring problem. Here are a few things to check:

1. Check the door latch: The door latch is what holds the door closed and triggers the door ajar switch when it is opened. If the latch is worn or damaged, it may not be able to hold the door closed properly, causing the switch to trigger the door ajar light. Try lubricating the latch with a silicone spray and see if this helps. If not, you may need to replace the latch.
2. Check the wiring: There may be a wiring problem that is causing the door ajar light to come on. Check the wiring going to the door switch and make sure there are no breaks or damage. Also, check the wiring going to the body control module (BCM) and make sure there are no issues.
3. Reset the BCM: If you have checked the door latch and wiring and everything looks good, you may need to reset the BCM. Disconnect the negative battery cable and leave it disconnected for about 10 minutes. Reconnect the battery and see if this helps.

If none of these steps fix the issue, you may need to take the vehicle to a mechanic or dealership to have it diagnosed.

The door switch doesn't go to the dome lights , the switch (door ajar switch ) is an input to the SMJ - smart junction box or body control module take your pick .
Principles of Operation
When the SJB detects a request for lighting, it turns on the interior lamps by supplying power to the lamps. The request for lighting can be an open door signal from a door ajar switch, an interior lighting on command from the instrument panel dimmer switch or an unlock command from a remote keyless entry (RKE) transmitter.
The door ajar switches are hard-wired directly to the SJB. The 2 door ajar switches are normally closed when the doors are closed. The decklid ajar switch is normally closed when the decklid is closed. All door ajar switches receive voltage from the SJB and each has its own ground circuit.
The instrument panel dimmer switch receives a ground signal from the SJB. The instrument panel dimmer switch provides variable resistance for backlighting the instrument cluster and a toggle ON/OFF function for the interior lights.
The RKE receiver is contained inside the SJB. When the SJB receives an unlock request from an RKE transmitter, it unlocks the doors and turns on the interior lamps. There could be DTC'S diagnostic trouble codes stored in the SJB ! You can not access these codes with a OBD2 code reader , need a factory scan tool .
B1319 Driver Door Ajar Circuit Failure Go To Pinpoint Test D . B1327 Passenger Door Ajar Circuit Failure Go To Pinpoint Test D . B2021 Dome Lamp Input Return Circuit Failure Go To Pinpoint Test A . B2550 Dome Lamp Output Circuit Short to Ground Go To Pinpoint Test A . B2554 Dome Lamp Output Circuit Failure Go To Pinpoint Test D . Do you know B-codes -body control .
Your best bet is to take to a ASE certified repair facility or a Ford dealer .

Check door switch for misadjustment or failure. This is the switch at hinge area.

control module messing up?? change it..

It can be issue with faulty sensor or a wiring issue.Troubleshooting is required.
Click the help link shown below:---
Door Ajar Light and Dome Light Remains ON? http://whoisbyme.blogspot.in/2012/06/2003-mercury-sable-door-ajar-light-and.html
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Door ajar light stays on? http://technoanswers.blogspot.com/2012/01/door-ajar-light-stays-on.html

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Thanks.

Either the problem can be solved by this: 1. Replace the spring at the injection or carburetor area. The spring pulls the pedal backwards so that it can be used as normal as it is. 2. Detach the pedal cable and try spraying it with a WD-40 anti-rust spray inside. This solves alot of cases in most pedal issues.

It sounds like there is a short somewhere. Either a bad ground, pinched wire going from the door to the fuse box, or a possibly a bare wire shorting out onto something. You say that the door adjar light and the door locks are affected. Check the door switch and make sure that it isn't broken, shorted out or sticking. Function test it. If you disconnect the door switch and take a test drive does the problem still exists? Yes? Disconnect the other side. Did that cure the problem? Yes? Replace as necessary. No? The problem isn't in your door switch(s). So that much has been ruled out. These are just some areas to start trouble shooting. At first I immediately thought "Door Lock Switch," but when you mentioned that the Door Ajar light keeps going on along with the light then it leads me away from the Controls and more towards the Door light Switch usually in the jam of the door, but you didn't mention the year, make and model, so location of the switch is obscure. If the door locks are switching on and off and the door adjar light is in harmany with it then make sure the door is secure, not loose when closed allowing the door adjar switch to break the connection. These are the areas I would investigate first. Is there a significant amount of slop in the door when you push and pull on the door like it isn't secure? These are some areas to take into consideration when trouble shooting.

Good luck. I hope this helps narrow things down for you.

there is a switch in each door that senses the door is open, it is called the door ajar/courtesy light switch (imagine that), they stick and have this problem, replace it.

What happens when you remove both switches, and wires? What happens when you use a jumper wire acros both wires, on both doors?

it could be a ground problem from batterie to car body or engine to car body make sure you have good ground at vehicle body