Just bought a 2003 Mustang. The interior light does not come on from the door or the headlight switch. It will work from the switch on the light itself. May not be able to answer this without more information but thought it worth a try. Wondered if a PO disabled it for the nuisance factor ,, and if so .. what would be the most likely way to do that. Just a wild guess
Thanks,

 

The switch on the light controls the bulb for the map light. This bulb is not the same as the one that comes on when you open the door, that bulb is in the middle of the light. It is possible one of the door switches failed keeping the light on, and the previous owner removed the bulb. Or the bulb is burned out.

 

+1^ Probably the bulb.

IIRC, the door switch and the headlamp switch send power to the dome light independent of each other. It would be unlikely for both circuits to fail simultaneously. Remove the lens and check for power (or install a new bulb) to confirm.

 

Spot on Dragul .... Light is on all the time .. . bulb removed. . Probably a door switch. . That seems the most likely.. Now the fun of accessing it .. and which door. .. On the older cars it was simple.. Not sure what I am getting into with this .. . Any thoughts would be appreciated. .

 

My guess would be the drivers door, as this door gets the most use.

 

Agreed. I too would suspect the driver door, though the headlamp switch is still a possibility.