Date:         Sun, 14 Nov 2010 02:06:22 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Ignition switch -- construction
Content-Type: text/plain; charset="us-ascii"; format=flowed

The key-in switch would please Rube Goldberg or that British fellow.

But other than that, it's quite a clever design.  It's a
break-before-make switch with a cam profile built into the
perimeter.  The brass rotating contact has a cam follower on the end,
so it gets lifted off the 30 contact in between switch
positions.  Thus it makes wiping contact with the brass terminal ends
before the chunk of silver in the middle is lowered onto the silver
30 contact with a (very) slight rotating motion.

It is *not* snap-action, so the speed with which it makes and breaks
contact with the 30 terminal directly depends on how fast you turn the key.

On the one I just took apart (aftermarket MWO brand, all white
plastic)  the silver contact connected directly to the 30 terminal
was worn concave in the middle, a bit pitted, and the contact area
covered with black "stuff," parts of which had a burnished
appearance.  Some of it wiped off easily and some did not.  It's my
opinion that this represents contamination from grease used to lube
the switch moving parts, but I can't prove it.

Turning off your loads before switching off (especially big inductive
loads like the blower motor) would probably contribute to the
longevity of the switch as there would be less arcing between the
contacts as they open.

Yours,
David