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Can anyone here tell me how to check a brake light switch on a 2002 BMW E46 330i?
All other lights are working in the rear except for brake lights. Fuse was ok, and tail light shares same ground as the brake light. The switch is magnetic on the end, so not sure if its like a hall effect switch. the switch has 4 wires and believe it has power,ground and signal wires to a module. any help will be appreciated!
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my guess it you can check it like any switch using a voltmeter put one end to ground and check each signal wire if you get no ohm reading there check power should be 12v
Call me crazy, but I’m assuming you checked either the brake light bulbs themselves to make sure they’re not blown, or the elements on the bulb your brake lamps share with.
The brake light switch itself is usually mounted above the brake pedal. When the pedal is depressed, the switch closes the contacts and activates the brake lights. I’d look at a wiring schematic for your BMW and first determine what voltage you should see at the switch. Measure it there and if it’s good, measure it at the brake light bulb socket.
You might have an accomplice be available to step on the brake pedal once you know that switch is good, while you check for power at the lamp sockets. I think you’ll find the input to that is through the drivers side brake lamp and feeds through the trunk to the right, usually below the trunk lip.
Remember that circuit will not show any current until it’s energized by pushing on the brake pedal. Your problem could be as simple as two blown bulbs although I’d examine why that happened. OR, a bad switch or mispositioned switch, which is rare although it happens. Could also be a loose or broken connector either at the switch or at the bulb socket. My bet is switch.
MarkFound a recall on your car. The dealer should take care of it.
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