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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