Dear Contact no Contact

I agree this is a great reminder of the sensibilities of auto electric
diagnostics
love it - bookmarked

On Thu, Jun 15, 2023 at 8:11 PM Alistair Bell <ragnarhairybreeks@icloud.com>
wrote:

> Very nice!
>
> Love this post
>
> Ab
>
> > On Jun 15, 2023, at 8:35 AM, Tom Neal <tneal4242@gmail.com> wrote:
> >
> > 
> >>
> >> Richard Koerner <rjkinpb@SBCGLOBAL.NET>
> >> Subject: Microscopic corrosion on electrical contacts
> >
> > About 80% of electrical problems are contact related.
> > The circuit to an electrical device is:
> >
> > Contact in
> >       !
> > Device
> >       !
> > Contact out
> >
> > I verify contacts first before replacing parts.
> > Even light bulbs.   Do they rattle?   Can I see the blown filament?  If
> not, maybe contact?  I don’t even believe apparently dead batteries are bad
> until I’ve proved it with a voltmeter.
> >
> > At HP a guy taught a course “Contact 101”.  It was fascinating and went
> into the macro and microscopic world of contacts.  Materials theory.
> Actual equations.  Pretty cool.
> >
> > Most of our worst class problems at HP were…are you ready for it…contact
> related, usually opens but sometimes shorts.
> > Gold plated finger pore corrosion (need more nickel), micro connector
> contact with high current, squishy connector membranes between VLSI and PC
> board (torquing super important), flex PC finger connectors (good luck,
> don’t work), and throw in IC silver migration that opens up circuits.
>  Pile on top very slight salt contamination and a condensing environment
> giving an unwanted contacts between PC traces.
> > So why wasn’t I a mechanical/materials engineer instead of electrical?
> :-).
> >
> > Some key points from Contacts 101:
> > Movable contacts love to be occasionally exercised, which scrubs the
> surface micro corrosion.  (Many times an old Vanagon switch works the
> second time.)
> > As we know, non moving contacts do corrode with current going through
> them or even just sitting there.  A little dielectric grease, Vaseline, or
> one of my favorites swimming pool silicone grease (seals plumbing, hoses,
> etc. wonderfully, smooths assembly of parts, and reduces wear…magical
> stuff) will give some protection from oxidizing compounds and is a great
> idea.
> > Some contacts just wear out or corrode too much and need replacing. That
> Vanagon horn contact scratches without lubrication and I think only about
> half of mine is still there.
> >
> > Had a nasty intermittent open loop fuel injection for years on a ‘91
> Olds 98.  Something to do with the O2 sensor.  Replaced them, fiddled with
> the leads, etc.  Dealers and mechanics couldn’t find it.  Finally it failed
> solidly.   The O2 GROUND wire went to a post with the alternator support
> and other big items on it that heated and cooled.  Not a pretty place for a
> delicate sensor connector.  Design changed in subsequent years, thankfully.
> >
> > The worst problem my van has now is the wires going to the driver door
> are breaking due to 327K miles of flexing. An uncontact problem.
> >
> > So, yep, right on.  If long term contact reliability is wanted, get the
> corrosion off and protect the mating surfaces.
> >
> > Happy Vanagon repairing.  Tom
>

-- 
roger whittaker 604.414.6266

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