Date: Thu, 15 Jun 2023 20:10:35 -0700
Reply-To: Alistair Bell <ragnarhairybreeks@ICLOUD.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <ragnarhairybreeks@ICLOUD.COM>
Subject: Re: Contact in, contact out
In-Reply-To: <D94DA9DC-BC54-4D2B-BAC2-B19D5AFB87F6@gmail.com>
Content-Type: text/plain; charset=utf-8
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
| 
