by John Logan in the November 2003 RootesReview
The best way to fix the brake light switch is to wire in a modern, normally on, plunger type brake light switch. This type of switch is very important if you have cruise control, since it will turn the brake lights on and shut the control off as soon as you touch the brake pedal, rather than after the pressure builds up in the system.
There are many switches available at auto parts stores. I prefer the all metal ones with more durable mounting threads. Support the switch with a simple bracket from the under side of the heater box so that it is activated by the brake pedal arm. The further the contact point is from the arm pivot the better. Tap one wire into the green and purple wire that goes to the brake lights under the left side of the dash by substituting the original connector with one of the standard dual connectors. Connect the other wire to any green wire found under the dash. If the original switch is not leaking, it can be left in as a redundant switch.
Ed note: There have been many reports that use of silicone brake fluid will cause the original brake switch to fail. This provides a nice fix.