Trying to get my 68 Mustang back up lights working. They were pretty old and nearly falling apart so I rebuilt them by removing the lamp plug from the housing and installing new ones from a local parts store (the originals were 2 contact type and I replaced them with 2 contact type). This did not solve the problem of getting them to work. They are wired into 2 plugs located near the brake lights inside the trunk. I tested to see if it was my rebuild job that was causing the problem but it seems ok because when I put a postive and negative 12 V to the 2 wires, the light comes on. Are the 2 wires supposed to both be powered (and rely on the light itself to be a ground)? If the problem is not there, it must be at the switch, right? In the 68, there is a swtich mounted to the transmission that has 4 wires and runs up into the back of the dash. The swtich is actually a collar that turns as the transmission changes (not a swtich that the linkage pushes on). Is there supposed to be another swtich? Can someone offer some advice?

 

I can't tell you for sure about the 68 backup light switch, but on my 65, it is located at the rear of the tranny and the shifter linkage operates it. When I put it in reverse (manual) the switch activates the lights. I suggest that if you also have that same kind of switch, that you take it out and test it. If it is inoperative, then just simply replace it.