Dome light wont turn off

Sometimes the plug that goes on the switch overheats and melts . I've had this happen on 2 Darts in my lifetime. Replaced switch and plug housing. A lot of power goes through the switch and causes heat. Do the headlight relay kit after you repair your switch and plug housing.
Your housing may look like this.
switch_b325fbd8ffda6abf87c84de5ac2b6ecd6f6225fc.jpg