"Would you expect the brake lights to come on when the 2 wires are connected with a probe and the brake pedal depressed (or not)?" Yes. But you don't need the probe for that: the brake lights should come on when you short the two sides of the switch together (with the ignition on). It sounds as if one side of the switch is live, but I don't know what your probe does, so if in any doubt check the brake light fuse. Any recent work or other problems, and are all the other lights working? Have you got a multimeter, and would you like a wiring diagram? Jonathan