(Same as 64-65 Acadian) I saw this question on another forum and thought maybe it would be worth posting here. I don't recall this being covered here before.

If anyone is having trouble with front or rear signals on a 65 or 66 full size, there's a good chance it's the switch and it's repairable without buying a new one.

This is how the switch looks-



And this is what you see when you remove the white "horseshoe". The brass squiggly contact strip and brass pins (Index finger pointing to that area) were dirty on mine. I cleaned them up with fine sandpaper, a couple of tweaks on the brass strip to make sure the contact on the pins was firm enough, and it worked fine after that.