2003 Ford Mustang - interior lights won't go off

interior lights on the mirror wont go off

Switch may be broken.

Try spraying contact cleaner into each door latch to clean the light switch contacts.

The problem might be caused by a failing GEM. (generic electronic module)

Ford used these to control all sorts of electrical systems in their vehicles. Including the interior lighting.

In the mean time what I would do is either unplug the rear view mirror, or remove the lamps for the lights, and see if any other interior electrical systems start acting goofy.

If they do, start thinking GEM.

Tester

The door latch switches were notorious to fail and the GEMs were nearly as big a problem. The door latch switch is easy to replace once the door trim is removed.

I would think that if there were a problem the door switch, all the interior lights would be on.
Not just the lights on the mirror.

Tester

If it is a convertible the dome lights are in the mirror.