The brake light switch is mounted in the master cylinder and ensures that the brake lights come on during braking. If your car is equipped with it, it measures the pressure difference between the front and rear brakes.
There are three versions in total: a two-pole switch with a partition for older years and without a partition for later years which are connected by a plug and finally a three-pole switch.
With a three-pole switch, there are always two switches fitted that control the brake lights but also measure the pressure difference. If there is a warning light on the dashboard, you are dealing with a three-pole switch that measures the pressure difference between the front and rear brake system.
Volkswagen introduced this warning system at the end of the 1960s, it was first applied to the more luxurious versions and in the mid-70s it became standard on all models.
With some switches you can choose between two qualities: quality A has a life span equal to that of the original, while quality B can show early leaks.
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