Ford Taurus SE 1999. Dome Light - Door Ajar indicator problem. This is an intermittent problem, hence far more difficult to isolate. OK. I will be thorough in describing this "set of problems" as I do not know if they are related or not. About 2 years ago the "Low Coolant" light came on. It never went off. Whether coolant level is low or not, the light stays on. (no biggie, just irritating) Then the seat belt unfastened indicator light malfunctioned. It comes on when you start the vehicle and stays on for awhile. But whether you fasten the drivers side seat belt or not, it goes off. (not a big problem and I included it in case these are all related.) Lastly, and most frustrating, is the door ajar light. Sometimes it works perfectly, and works well for days. Then the dome will stay on. The door ajar light will stay on. You can't lock the drivers side door while this is occurring, as the door will immediately unlock (only while driving). If you park and turn off the car the dome light will stay on. I will open and close the door to no avail. One night, I had to disconnect the battery to keep it from going dead. Then mysteriously, it will start working fine again, and sometimes for days. One time, while it had been working correctly for days, I got out of the car and the dome light did NOT come on. I got back in the car and started it. I left the door open, yet the dome light stayed off and the door ajar light was NOT lit. The car thought the door was closed. This only happened one time. Often, when driving with the door ajar light on and the dome light on, the car will make a audible "bing" and the dome light and ajar light will go off. The other 3 doors have zero problems. I lubed the driver's side door (wd40) and made sure it is aligned correctly. I made sure it fully latches. I do not know if it's a coincidence or not, but the door ajar light, seat belt light, and low coolant light are all located in the same area of the dash. All three indicator lights may function with the same logic controller, but I really don't know. Should I invest in a code reader? Any ideas? Please help, because when that door ajar light fails to go off, the dome light will drain the battery. During the day, it's hard to notice the dome light stayed on. I know a dealership will charge me a boat load to troubleshoot this with no guarantee of resolution. Plus, every time I've tried to demonstrate this problem to someone, the car's lights work fine. Weird. Thank you, M.N..