One of the problems I had early on with the car involved replacing the brake light switch. This is a little beast that's located at the top of the brake pedal. The switch is a circular housing with a metal arm that rotates, and it's spring-loaded. You mount the housing onto a bracket and make sure the roating arm is fully cocked (the spring is taut) and resting on the brake pedal rod. When you push the brake pedal, the pedal rod moves toward the firewall, and the arm on the switch rotates out with it. As the arm rotates, a switch inside closes and feeds electricity to the brake lights.
I hate that switch. I'll be polite and simply say that I don't know what the engineer who cooked it up was thinking. But:
it's a pain to mount it and set it so it works properly;
it's prone to stick in the OFF position because it gets old and gummy; and
it takes the full brake lamp current, which tends to burn up the contacts inside the switch.
My old man was an electronics tech, so he drew this up when we replaced the switch the third time. The way to read it is this: originally P1 and P2 tied directly together; i.e. full powered flowed through the switch. My father cut this and inserted a relay.
I'd forgotten all about this until I found this in one of his notebooks. Must have worked well because I haven't had to mess with the switch since then.