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Brake Switch Install

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Hello- brake lights not working properly (a flicker then nothing) Read 5 pages of forum "search" topics and still have 2 questions: 1) is there any trick to installing the new brake switch? does the plunger need to be adjusted, or what position should it be in when placing and then twisting it into the bracket 2) will all work properly if 1 bulb is out of the center brake light (the bulb holder on one bulb vanished as i was removing)

Thanks all, and love the site!

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Here is the process from the service manual:Brake light switch settingThe switch travel of the brake light switch is designed so that the brake light lights up before braking pressure builds up. The switches are self-adjusting and are mounted in a bayonett lock in the pedal block by turning them through 90°. By way of its self-adjustment function, the switch compensates for the tolerances in the pedals during initial assembly. However, if the switch is "overpressed" during work on the pedals or on the brake unit, the switch travel or pedal travel up to the switching point is lost.The consequence: The brake lights are always on or flicker when travelling over bumps. In vehicles with cruise control, the cruise control can be deactivated as a result of vehicle vibrations under certain circumstances. Therefore, the switches must be readjusted after any work in which the brake pedal is moved out of its "normal" position (for example, work on the pedals or on the brake unit).Checking brake light switch setting (No. 1)The pedal must move a perceptible distance of approx. 5 to 10 mm before the brake light lights up.At the same time, check (make sure) that the brake light lights up before the pedal meets perceptible resistance or before brake pressure builds up.Adjusting switch if pedal travel is too smallThere are two possibilities to adjust the switch if the pedal travel to the switching point is too small.1st possibility:- Press the brake pedal and pull out the switch plunger.- Release the pedal. Check adjustment2nd possibility:- Release switch by turning it 90° and pull it out of the installation opening.- Pull operating plunger out of the switch as far as it will go.- Reinstall the switch.When installing the switch for the first time, it is essential to press it vertically against the bearing surface. It will otherwise not be possible to lock the switch (90° turn), even if great force is exerted.Note: A play-free fit of the switch is no longer ensured after it has been installed and removed several times. The switch must be replaced by a new switch as soon as it perceptibly "wobbles" in its receiver.Adjusting switch if pedal travel is too largePress pedal and press plunger into the switch by one notch (audible click).The pedal travel to the switching point then decreases by approx. 3... 4 mm.Then check setting again.

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  • 2 weeks later...

it was the break light switch, and all worked well. the toughest part was getting positioned to twist the old switch out (kneeling beside the car worked great), and a beast to get into position to twist the new switch in (kneeling beside the car again). Finally, after much pressing and twisting, i pulled the new switch out, used a screwdriver to create a bit of additional room for the brakelight holder by spacing the plastic tabs on the switch a bit, and voila...twisted right in. Thanks forum

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  • 1 year later...

Hi everyone.

A couple of days ago, the PSM & ABS warning lights lit up on my 2001 Carrera.


A quick search on this Forum suggested a faulty brake pedal switch.  Checked my brake lights and sure enough, no lights so a faulty switch is definitely indicated. After about 30 minutes of twisting my body under the dash, managed to get it out.  Sure enough, the switch has an open circuit. 


Bought a new switch and plugged it into the harness.  Tested the plunger on the switch to see if the brakes lights work - but they did not.  However, no PSM/ABS lights showing which is an improvement.  Seemed odd to me but I have seen stranger on this car so I press ahead.


Another 30 minutes of twisting my body under the dash and finally re-installed the new switch under the pedal.  But now the PSM/ABS lights turn on again and still no brake lights!  Back to square one!


Removed the switch (now it takes me only 5 minutes to twist my body under the dash) and check it out.  Checks out perfectly. And NO PSM/ABS lights with the switch plugged in but not installed under the pedal.  Hmmmm.


Check fuses and all the usual stuff.  Everything fine.  Thought about the brake light bulbs but what are chances of all 3 brake lights burned out all at once???  Surely at least one of them should be working so I can at least tell whether the brake light circuits are OK.   Seriously considering taking the car to the dealer.


Reinstall the switch under the pedal (I can now do that in less than 30 seconds of twisting).    Check the driver side brake light bulb.  It's burned out!  Check the passenger side bulb.  That is also burned out. Check the centre brake light - that one is OK.  So why don't I at least have a centre brake light when I press the brake pedal???


Replace the driver side bulb.  But still no brake lights anywhere!  Remove the new bulb and check it out.  Nothing wrong with it.  So I replace the passenger side bulb and suddenly everything works fine, including the centre brake light!  And no ABS/PSM lights!  Everything fine!!!


Question.  Are the circuits really designed so that if one brake bulb fails, none of the others will work?  Doesn't make sense to me.


Lesson 1.  Do the simple things first, eg. replace ALL bad bulbs before testing. Though I still don't understand why one dead bulb suppresses the other two brake lights AND turns on the ABS/PSM warning lights.  Or perhaps this was just some random weird chain of events!


Lesson 2.  Amazing how something that originally takes 30 minutes can be done in 30 seconds with a little practice!

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