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Re: brake light switch failure analysis

To: "Glen Byrns" <grbyrns@ucdavis.edu>, <spridgets@autox.team.net>
Subject: Re: brake light switch failure analysis
Date: Fri, 4 Jan 2002 16:18:13 -0800
Interesting analysis Glen, bu I think you missed the real problem...

... you'll notice right after you painted yours in...

Bright yellow paint!

After all, Frank has the most problem with them...'-)

Gerard

At 3:08 PM -0800 1/4/02, Glen Byrns wrote:
>So why do the modern day replacement brakelight switches fail?
>(fluid pressure activated type, like in the bugeye)
>
>Mine went after two years, so after putting in a replacement from
>"Interpart" of England, I cut apart the old one and checked out its guts.
>
>The rubber diaphragm was intact and free of any leaks yet there was brake
>fluid on the 'dry' side of the diaphragm.  This had caused a dark deposit to
>coat the contacts and the disc that is pressed to the contacts by the
>diaphragm when you step on the brake.  With both parts of the switch covered
>in this dark film of 'stuff', there was NO current flow through the switch.
>The clamping surfaces of the switch were clean and free of any burrs or
>particles that might have created a leak.
>
>Near as I can tell, it appears that the crimping process that closes the
>body of the switch does not apply enough pre-load to compress the rubber
>diaphragm and completely seal the switch.  In time brake fluid leaks around
>the rubber diaphragm and contaminates the contacts until they no longer
>conduct electricity.
>
>Speculation:  Old switches used a different rubber formula that did not
>produce any 'black stuff' even when a bit of fluid got around the seal, so
>they worked even when contaminated.  OR...  the new ones are not crimped
>shut with enough force to ensure a fluid-proof seal.
>
>Regards,
>Glen Byrns
>'59 bugeye
>'59 Morris Traveller (Winifred)

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G G              Gerard Chateauvieux
 E A
  R R        pixelsmith@gerardsgarage.com
   A A
    R G          Pixelsmith  on  Duty
     D E
      S      http://www.gerardsgarage.com

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