Date:         Sat, 23 Oct 1999 16:46:22 -0400
Reply-To:     EMZ <vw4x4@FYI.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         EMZ <vw4x4@FYI.NET>
Subject:      Re: Heater fan switch
Comments: To: David Beierl <dbeierl@IBM.NET>
In-Reply-To:  <4.2.1.10.19991023153554.06d16550@127.0.0.1>
Content-Type: TEXT/PLAIN; charset=US-ASCII

Smoke is a major contributer of contact resistance in vehicle. I would
not be suprized if the vehicle was owned by a heavy smoker at one time.
Also most switches should not be switched slowly. The contacts are made to
slap closed witch wipes and cleans the contacting surface.

            Eric                   86-VW4x4
            vw4x4@fyi.net          72-240z
            Pittsburgh, PA USA     1936-Chrysler


On Sat, 23 Oct 1999, David Beierl wrote:

> At 13:05 10/23/99 , Per Lindgren wrote:
> >I dissected the old switch, and it was melted solid. I don't know what caused
> >this, but the fan ran much better with the new switch than it did with the old
> >switch. If another meltdown happens, I guess I will have to investigate
> >further.
>
> I know!  I know!  The switch is made (thank you VW) of thermoplastic, and
> carries 12 amps.  When it gets a bit of contact resistance the contacts
> heat up, the plastic gets soft, the movable contact presses the fixed
> contact down into the soft plastic -- voila, it has just built itself a
> little playpen.  The contact pressure is less, the resistance is more, the
> contact gets hotter yet...
>
> I *love* relays...my switch on high speed is now supplying all of 100 ma or
> so to power a relay that feeds the fan from a dedicated circuit.  At lower
> speeds it has no trouble driving the fan itself.
>
> david
> David Beierl - Providence, RI
>   http://pws.prserv.net/synergy/Vanagon.htm
> '84 Westy "Dutiful Passage"
> '85 GL "Poor Relation"
>