Hello and welcome to Just Answer. I will try and assist you with your question.
It would be very helpful to know what year, make and model of car you are working on.
If I had to guess it would be a problem with the dimmer switch for the interior lights.
2005 chrysler sebring sedan 4 cyl.
OK just a second while I look at some info.
OK this circuit does run through the body control module so there could be an issue there. I would try moving the dimmer switch back an forth and watch all the lights. They should dim and brighten smoothly. If they don't then I would replace the dimmer switch. If they do but you still have the problem it will take a scanner with capability to access the BCM to check it out.
ok thank you