That was the same story with mine. After taking it apart and putting it back together, it now works on the door setting when the tailgate is opened. A bad ground perhaps, or a lose connection. My mid cabin dome is still not working with any door opened. I'm wondering if one bad driver's switch would effect all the others. Hmmm...
Tail gate/cargo light, when in the "door" position, is activated by a switch that's part of the tailgate lock assy. If you open the access panel (remove the screws) in the center of the top of the tailgate you'll see a wire (green w/ white or yellow stripe) leading to a contact. Try spraying w/ WD-40 to free up the contact. Otherwise just use the "on" setting.
It's also possible that the green w/ white wire could have broken due to fatigue with the hatch opening/closing and needs to be replaced. A continuity check from the wire in the upper tailgate and the wire where it connects to the light should confirm if it's still conducting. It's easy enough to use the existing wire to pull a replacment behind the headliner and through the rubber connector if need be.
That's interesting. Turns out I have a more profound problem with this light. It's fine in the off and on position, but the door setting is messed up. The light will come on dimly, accompanied by an illumination of the rear defrost switch button and a buzzing from the fan motor.
Yep, probably a grounding issue - the wire from the switch to the light has fatigued at the hatch hinge. You can drop the light and unplug the lead to the tailgate and not use the "door" setting or try to fish a new wire through the headliner, rubber raceway and hatch.
I just leave mine in the off position all the time just incase of the time when my door does not close all the way and the light might not have not turned off. That way my battery will be good when I get back to my truck. It makes the day better that way!!
Super old thread, but it helped me. I was having an issue with the rear cargo light on my fj62. It would turn on, but when set to hatch open mode it would do crazy stuff like turn on the blower fan like another post mentioned. I just unplugged the wire from the rear hatch latch and just have it in on/off mode. I think something in the latch is broken causing the issue.