Map Lights On Bottom Of Rear-view Mirror

I have a 2003 Rodeo and I noticed that the map lights on the bottom side of the rear view mirror come on by themselves. (The car has been sitting idle under the carport for over 24 hours.) I checked to see if a door was ajar or the lift window on the back may be ajar but all was closed. I unlocked the doors and got inside and the ceiling light came on (as usual) and the map lights stayed on as well. I depressed the button for each map light to turn them on and the light increased about 10% but when I pressed the button again to turn them off the light decreased about 10% but still continued to remain on. I exited the car and locked it and the lights still stayed on. Any ideas?