I am having this issue on our 2006 Chevy Silverado 2500HD with 6.6 diesel crew cab which we use to tow our 2005 Keystone Montana 2980RL. The front dome light comes on when either the front or rear doors are open, but the rear dome light do not come on when any of the doors are opened. Both the front and rear dome lights do come on when I use the dash light switch to turn them on.
Anyone have any ideas as to why? I haven't had time to try and troubleshoot the problem yet.

 

The rear seat overhead light bulb burned out - duh.. There are three bulbs over the rear seats, two with a push-on/push-off switch, one on each side and a center bulb controlled by the doors. Easy fix once you know what the problem is.