----- Original Message -----
From "Geoff Branch" <gjbranch at mediaone.net>
To: "Glen Byrns" <grbyrns@ucdavis.edu>
Sent: Friday, January 04, 2002 10:03 PM
Subject: Re: brake light switch failure analysis
> Mine conked on the Mini and I bought one from the usual suspects. NFG. Both
> would make contact if I pushed on the wet side with a punch. One of the Mini
> guys told me to fill it up with vaseline. ( I'd always wondered how the bubble
> that must be on the wet side got out and this was supposed to be the
solution.)
> That didn't work either. Finally I went to the local supply house and bought
a
> generic one and it is fine. Only about 2 months on it though. And if you
think
> bleeding brakes on a Meejit is bad....try a Mini....oh.
>
> Geoff Branch
> '74 Meejit "Yellow Peril"
> '72 Innocenti 1300 Mini
>
>
> ----- Original Message -----
> From: "Glen Byrns" <grbyrns@ucdavis.edu>
> To: <spridgets@autox.team.net>
> Sent: Friday, January 04, 2002 6:08 PM
> Subject: brake light switch failure analysis
>
>
> > 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)
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/cgi-bin/wilma/spridgets
|