I had both switches in the same VW tandem M/C go out, but replaced neither. One malfunctioned such that the the brake lights stayed on and the switch insulator melted a little. I disconnected the wires from it. The other stayed fully functional until after I changed to silicone fluid. It too stayed installed. It would pass enough currrent to run a relay, but not to light the brake lights. The contacts in those switches run "wet" sooner or later. Apparently silicone fluid interferes with the electrical contact effectiveness in a way that conventional brake fluids do not.

But I have never had a brake cylinder or caliper leak or malfunction since rebuilding (or not) and changing to silicone, unlike with conventional fluids. I suggest either mechanical switching or using a relay activated by the hydraulic switch. If I were reinventing wheel cylinders and calipers, they would all have drains on the bottom like radiators and engine blocks do.

Charles Greenlaw, Sacramento Cal