Read the OP’s previous post back on Sept 4 about the lights dimming after getting a new battery and a new alternator. He says he drives about 250 miles a month.
The OP needs to find out if there is a parasitic load drawing power from the battery when the car is parked and “off”. He mentioned an aftermarket radio was installed.
A chronically undercharged battery will make an alternator work harder and that will make the headlights dim more when things like the cooling fans cycle on and off. There could be a short somewhere or another fault in the wiriing that is drawing off power from the battery.
The '02 Sebring is one of those cars that gets expensive due to a lot of repairs as they age. The OP might want to look at replacing this one before it becomes a money pit for him.