1998 Ford Taurus Door locks,interior lite

Check the switch like this: DOOR LOCK SWITCH 1. Remove door lock switch. See DOOR LOCK SWITCH under REMOVAL & INSTALLATION. With switch in released position, continuity should not exist between terminal No. 4 and terminals No. 3 and 6. See Fig. 3 . 2. Press switch to UNLOCK position. Continuity should exist between switch terminals No. 3 and 4. Press switch to LOCK position. Continuity should exist between terminals No. 4 and 6. If continuity is not as specified, replace switch.

Another problem could be the wires where they pass from the door to the car, bend, and over time can break. check for that. If nothing turns up, you need to scan for trouble codes with a Ford capable scanner. Or chance it's the GEM(Generic electronic module) Aboutt 200.00!

I own an 98 Taurus. I had this problem developing when the car was three years old.The dealer could not find the solution. I searched extensively the ford boards and the technical bulletins and found the explanation. All door locks has a switch inside to tell the light control module that the door is closed. When that switch is not working properly (is blocked open) the module interprets that the door is ajar and the light stays on.Of course the people try to close the door better to slam it and that works sometimes by dislodging the switch, sometimes the switch remains blocked open. Try this, buy a can of WD-40 insert the straw in the lock (not the key lock but in the triangular opening where is engaging the door post stud) and spray working the lock by opening and closing the door repeatedly. That helped me.