Date: Sat, 24 May 2003 18:12:47 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: front heater rebuild webpage?
In-Reply-To: <20030525020445.44126.qmail@web41011.mail.yahoo.com>
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At 10:04 PM 5/24/2003, Joel Cort wrote:
[Parenthetical note -- Joel, removing the blower *motor* from the blower
fan and housing itself is a good deal harder than you've indicated on your
page (though there's no setscrew). I've written stuff a couple times
that's in the archives, and I'll collect and pass it on if I get a chance...]
>Hi Roger,
>You are obviously looking for David Beierl's pictures and info.
I *wish* I had pictures. Next time, God forbid, I have one open I will get
some, as I now have a suitable camera. However, the free-swinging flaps
I've written about and which are mentioned in passing at the bottom
http://www.knology.net/~vw/dash/ are easy to find if not so easy to fix,
and the symptom they produce is very characteristic: If you get good ram
air but poor output from the blower (blower motor running normally and not
spitting out pieces of mouse nest) it is almost certain to be a problem
with one or both of these flaps.
They are about 4"x6" and made of thin plastic similar to the rest of the
case. They're located in the wall that separates the input from the output
side of the blower, on either side of the blower; and they swing open
toward the output side. Their purpose is to allow ram air to pass into the
system without having to pass through the blower which would reduce the
flow; but also to prevent the blower output from circulating right back to
the input. Therefore they are free-swinging, very light, and operate on a
small pressure difference (or should). When the heater box is in operating
position they hang down vertically, swinging from molded pins at each end
supported in little clips molded into the housing. They have a very light
thin foam coating on the sealing side which is not necessary to renew, you
can just rub the remains off with your thumb to make a reasonably smooth
surface.
So: in normal operation, the breeze coming in from the external intake
shoves them open to a limit of maybe 30 degrees and passes directly through
into the interior, even at quite low speeds. However if for some reason
the wind should be such that air is going backwards through the system,
they will remain closed. If they are open and you start the blower, as
soon as the blower makes enough output that it's driving some air back
through these openings, the flaps close and remain closed so long as the
pressure in the output side of the box is higher than the pressure from ram
air coming in. In my experience running the blower at high speed will
cause this at least up to 60 mph or better unless there's a gale of wind
blowing from ahead.
The problem is that they are in an unfiltered intake stream which may
contain dust and grit; and VW engineered them for cheapness and easy
assembly instead of for longevity. The flaps hang suspended from the
aforementioned clips *which in normal operation are open at the bottom* so
that the flaps may be snapped into them easily. This means that the area
that should be bearing the primary support load doesn't exist, and the load
is taken instead by the clip at something like 45 degrees to either
side. They can't close the opening too much because otherwise something
would break when the flaps are clipped in during assembly.
In consequence, as the flaps swing open and shut through their restricted
travel, the pins wear into a triangular profile, and the clips into a
matching funnel shape. At some point down the road (short of 180,000 miles
in my sample of three) one or both flaps either sticks open, or simply
falls out of the clip entirely.
The cure is simple -- rehang the flaps so they work correctly -- but not
easy, because working room is very restricted. What I've done is to build
up the pins with filled epoxy if necessary (metal replacements would be
better but harder), then remove all or part of the plastic clip as seemed
indicated, and hang the pins from wire supports melted into the
plastic. I've done two -- on the first I used wire brads heated and shoved
through the box (which is very narrow at this point). On the second I
worked up some sort of staple shape which I thought was clever, and which
was inserted -- I think -- directly over the pins. I seriously wish I'd
gotten pictures of that one, sigh. Results in both cases were excellent --
but you must make sure before reassembly that the flaps swing absolutly
free and don't stick in any position. I don't know what will be the effect
of the plastic pins bearing on the wires. I suspect they will wear at
least as rapidly as the original arrangement, but perhaps they won't. Any
tribologists with an opinion on this?
david
--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
