1978 Ford F-100 rear lights

Hi, I'd have to check the bulbs-- bulb sockets-- wiring circuits at the rear. Brown wire carries voltage to tail lamps. The circuit goes hot when you turn on the headlite switch. Black wire is ground. The lite switch is in the diagram.

BE SURE to properly ground!! I have an 1981 F100 and the brake lights didnt work when i bought it, i had to run a chassis ground to them.