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Subject: RE: TWL: DC Switches
From: Arild Jensen (elnav@XXX.XXX)
Date: Wed Dec 18 2002 - 14:16:23 EST
-----Original Message-----
BTW - This is why the bilge pump switches fail so quickly. They build up
weld deposits on each activation of DC current. If not designed with
expensive contacts and advanced engineering they fail. Apparently the
manufacturers cannot match the technology and price boaters are willing to
pay.
REPLY
This is one reason why the old mercury switches were so good.
Mercury being a liquid was "self healing" after each contact break.
you did not end up with any burn spots to create higher contact resistance.
Unfortunately, because mercury is toxic when ingested; the use of mercury in
any application was prety well outlawed by the well intentioned safety and
environmental protection people.
I have disassembled a number of newer Rule switches that failed.
Now they use a metallic contact which does burn when breaking currrent flow.
Even worse, the switch housings are not always perfectly sealed as was the
old mercury switch so they sometimes leak and corrode. Result even more
failures!
The only reliable switches now cost about $100 instead of $15.
Arild
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