My 94 6.5t 3500 is having electrical issues. I have no back up lights. But brakes and turn signals work fine. My third brake light that's on the back of the cab doesn't work. Either do my cargo lights back there. Think the kid that had it before me screwed it up when he put the tow package on. Is there a fuse is the panel for the third brake lights and cargo lights. And the cd player only plays music out of rear drivers side speaker. I looked at the wiring and its a big cluster, where do those wires go to? Cause I only get power off the constant and actual power. Not out ofany other wires. Please help. And thank you for anything in advance

 

check reverse light switch could be stuck closed.