ChatterBank1 min ago
Brake light failure
Answers
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For more on marking an answer as the "Best Answer", please visit our FAQ.You have not said what sort of car, but here goes. Two types of switch. One is operated by movement of pedal arm and is attached near fulcrum of lever. The switch is kept open by the spring holding the lever arm in normal position but closes the circuit when foot moves pedal arm. Thjs seems unlikely to be the case in your car as you say lots of pressure = lights on.
Second sort work from hydraulic pressure and are located on the brake pedal cylinder or more likely on the vacuum servo box. You cannot fix these switches when they go wrong, you have to replace them. Not expensive, but may require brake bleeding after fitting new one. They look like mini spark plugs that screw in and have two wires (sometimes only one) attached at the top.
You can confirm that you have located the right gizmo by unplugging then shorting out the wires briefly with the ignition on (no need for engine running) and see if brake lights come on. Mirror handy for checking this! If only one wire then connect it to metal of car briefly.