Ford: 99 ford taurus alarm issue, door latch, ford taurus

Question
My door ajar light has just begun to go on and off at will.  With that the light stays on.  I've been told using WD-40 would help resolve this issue.  But the weird thing--I've had my car 5 1/2 years--never had an alarm that I knew of.  Never set it, it never went off, there was no hint that I even had an alarm.  A few days ago, the 'alarm' starting going off--horn blowing, lights flashing, and it happens whether the doors are locked or unlocked.  Help!

Answer
There is a couple of things that I can think of trying before going to the dealership. try getting a factory ford key fob (Remote) and program it to your car... this can be done bt doing what is called a "Key cycle" (From the off position rolling the key to the on position is one key cycle... the second will be rolling the key from on to off to on... etc... after 8 key cycles the doors will lock and unlock... this lets you know that you are in programming mode... press the lock button on the remote... the locks on the car will lock and unlock. turn off the ignition and they will do that one more time... now try unlocking the car with the remote...

you migh talso try replacing the door latch in the drivers door (Pretty sure that is the one that you are having trouble with... ) if you can't replace it unplug it and see if the alarm keeps going off... other than that you are going to have to go to the dealership to have the car looked at.... sorry  if this doesn't help...