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67 Bug Has Two Brake Switches - Why?
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xrotaryguy
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PostPosted: Thu Aug 15, 2019 8:59 pm    Post subject: 67 Bug Has Two Brake Switches - Why? Reply with quote

I have two brake light switches on my 67. The wiring diagram shows they're wired in parallel. Why would that be?

Also, one of my switches closes when I press the brake. The other does not. Is this correct? Or do I have one bad switch?

The wiring in this car is a mess. I intend to replace it all! But I want to understand this circuit better before I dive in.
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Pruneman99
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PostPosted: Thu Aug 15, 2019 9:01 pm    Post subject: Re: 67 Bug Has Two Brake Switches - Why? Reply with quote

It's a redundant system in case one fails
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xrotaryguy
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PostPosted: Thu Aug 15, 2019 9:03 pm    Post subject: Re: 67 Bug Has Two Brake Switches - Why? Reply with quote

Simple enough. Thanks.

Makes perfect sense considering one has failed haha.
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sjbartnik
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PostPosted: Fri Aug 16, 2019 8:04 am    Post subject: Re: 67 Bug Has Two Brake Switches - Why? Reply with quote

To expand on what pruneman99 said:

The brake system in a '67 is split into two independent hydraulic circuits.

That way if you have a failure somewhere in the system (like a hose rupture or a wheel cylinder blowout) you will only lose braking on two wheels while the other hydraulic circuit will continue to function and provide you with some braking ability (though much reduced).

The brake light switches are operated by hydraulic pressure. If there is no hydraulic pressure in the system, then the lights will not work.

The way VW has designed it, the system is set up so that even if you completely lose the hydraulics in one circuit, both brake lights will still work, as there is one switch per hydraulic circuit.
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xrotaryguy
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PostPosted: Fri Aug 16, 2019 9:47 am    Post subject: Re: 67 Bug Has Two Brake Switches - Why? Reply with quote

Great. I guess the alternate solution is to put a switch on the pedal. Then the brake lights work regardless of if one circuit has lost fluid.
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Cusser
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PostPosted: Fri Aug 16, 2019 11:37 am    Post subject: Re: 67 Bug Has Two Brake Switches - Why? Reply with quote

xrotaryguy wrote:
Great. I guess the alternate solution is to put a switch on the pedal. Then the brake lights work regardless of if one circuit has lost fluid.


Just get good-quality brake switches, easier and less expensive.
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