Door Ajar/Interior Light Stays On

From Taurus Car Club Maintenance and Modification Wiki

This is a common problem with the Gen3's. To solve it, simple spray some WD-40 into the door latch. It will release the stuck sensor, and fix the problem. Some owners have reported that after a few years of doing this, the WD no longer works. In that situation, try using some electrical contact cleaner in the door latch, followed up by compressed air if available.

Another common way of fixing this, and probably the best way, is to spray the latches with WD-40, and open and close the door several times to work it in. After waiting for that to dry, spray some white lithium grease into the latches and work that in by opening and closing the door several times. While WD-40 is good at cleaning, over time, more grease and dirt will return and adhere to the WD-40 residue. The white lithium grease will lubricate, and prevent the dirt from gunking up again.

For wagon owners, the rear hatch striker pin is a common problem. Here's what to do: Loosen the striker pin using the proper allen or torx key. Slide the pin the whole way to the rear of the car and then forward about 1/4". Re-tighten the pin and close the hatch. This should also help relieve annoying rattles from the rear hatch.