I have a 1997 f150, and when i put a bulb in the third brake lite socket, and press the brakes it dont come on, but my dome lite will, with the breaks pressed. When i open the door to the truck thd dome lite comes on and so does the third break lite, any help?

 

It sounds like worn wires where perhaps sheathing has worn and wires are crossing along the electrical relays somewhere. I have same year truck, thusly have the shop manual. I am not at home so I cannot look up the wiring diagrams n see and also troubleshooting for this issue.

 

Were would i start to trouble shoot?