Started having an issue with this about a month ago. I would get in the truck turn on the key and everything but the overhead would work correctly. Started checking all my connections throughout the truck and found nothing. It would work most days and then nothing for a day or 2. Thought about what I had changed on the truck resently and it hit me. My cab lights were leaking about a month ago so I had resealed them and with all the rain we had lately I knew that had worked. When the lights were leaking though I only noticed it because it dripped from the overhead. I pulled the overhead and the corrosion ways right in front of me. Alittle tim with a toothbrush, battery cleaner, compressed air and die-electric grease the problem has been solved.