The plastic Brake switch will perform well as long as the switch is installed correctly. Most problems occur when the switch is incorrectly installed. The Adjustment bolt on the frame must be adjusted correctly for operations and longevity of the switch. If adjusted correctly, the rubber cover will wear out before the switch. The following is a picture of the 1970’s brake switch:
Note the external connectors on the switch. I will reference them in the following discussions. The following is a picture of the switch with the rubber cover removed:
With the rubber cover removed you can see the internals. Note several parts in the picture: On the right of the picture note the button activator in the rubber cover. Note the switch internals in the plastic body. The following figure will define all the parts of the switch:
The part I call “switch” rides up and down the “slide”. In position 2, the brake light is on. In position 1, the brake light is off. When the brake pedal is relaxed or off, the “switch” should be in position 1 or off. The “adjustment bolt” should be in contact with the “Button Activator” such that the “switch” is in position 1.