This one has me scratching my head. I have a 97 Ranger. The truck is fairly basic, no power locks, windows, mirrors, AC. It does however have the 2 bulb dome light and bed cargo light (the two while lights beside the 3rd brake light.) From what I understand, the dome light and cargo lights should come on when the doors are open, but they dont. The dome light can turn on using the switch on the light itself. If I roll the dimmer all the way up until it clicks the cargo lights come on but not the dome light. Any ideas whats up?

 

Im not sure about a 97 yr.. but on my 02.. I replaced my dome light assembly with an early 2000 yr Mustang with has a dome light plus map lights and replaced the bulbs with LED bulbs, I also got a cargo light assembly which was an option on the 02 and also put LED's in it,,My Cargo light does NOT come on then I open the door..Only when I roll the switch all the way like u mentioned..

 

There is a door switch that when you open the door turns on the dome light. There is probably a fuse or a relay that controls it. The door switch could be stuck. Check the door ajar switch then the relay, and finally a fuse.

 

Blown Bulb?