Date:         Thu, 20 Dec 2007 19:54:24 -0800
Reply-To:     Brian Jarvinen <brianvwagain@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Brian Jarvinen <brianvwagain@YAHOO.COM>
Subject:      Inside the Air Flow Meter / AFM
Content-Type: text/plain; charset=iso-8859-1

Since I asked the list a question tonight, I like
to add things I've learned lately.

While working through a wire issue this fall,
(Hall Control Unit thread),
I learned all I could about the AFM and installed
the capacitor fix on it myself.

You should definitely note that the correct
capacitors are no longer available at Radio Shack
at all, but aren't that hard to order online
elsewhere on the web.

The instructions and photos out there are great
and were a big help. Ken Lewis sent along
a photo of the innards of his AFM, and when
I opened mine I noticed it was different.
(11/83 1.9L here). His had a jumper connected
to the copper arm that goes up to the copper
circle that the upper, pointed tip of the wiper
arm contacts, mine lacked this wire jumper.
Perhaps this was redesigned later
to improve conductivity?

I have some pictures of mine I could send out
to illustrate the difference but don't know how
to host a photo on the web.

I would also like to note here that I would not
advise removing the connector housing from
the body of the AFM. It is not hard to do, (four
small screws) but to
solder the capacitor in you do not need to remove
it. The thin arm coming up from the
wiper comes out with the four pin connector,
and this arm depends on proper tensioning to
maintain the signal. When I reinstalled my AFM
I couldn't start the van and the Bentley tests on
the connectors revealed a problem inside the
AFM - the point of the arm wasn't making contact.
A bit of bending and tensioning and all was well
again, but I could have avoided this all together.

Reading all of the archives on AFM questions over
the years revealed that the track can be repainted
with a specialty electrically conductive paint, but
the link to the supplier no longer works. Does
anyone know where to find some of this paint?

It was also wished for in one post to find a source
for a completely new Printed Circuit Board. Does
anyone make these? I suspect the "re-built" AFMs
that can be purchased have this track resurfaced,
rather than the whole PCB replaced?

I was unable to get my wiper arm moved very much.
I could only get one of the three screws out, they
are in tight. Drilling out the other two and
re-screwing
and moving them just enough to put the arm on a new
track
did not appeal to me. The 2 worn semi-circles on the
track seemed fairly wide already, already perhaps less
than 50% of 'virgin' track left and I wasn't confident
I
could get it to ride correctly on a fresh area - a
very small
adjustment.

So I'll either be hoping to find some of that paint,
or purchasing a professionally re-built AFM, or both.

There is also some talk in the archives of an
after-market
firm coming out with a re-designed air-intake box to
supply the ECU with the necessary information with
a more reliable mechanical system. Did this ever
happen?

And finally, this whole process has taught me where
an oddity to the idle has crept in. I notice it at
stop
lights now, definitely - it reminds me of running
without the Idle Stabilizer connected but not nearly
as much surging, and now the Stabilizer is in use.
I would have a pro
shop tune up the van once in awhile, with CO metered
and adjusted, but this wasn't the complete picture. I
now feel that as that track gets warn, the idle
deteriorates
just slightly - just enough to cause excessive
vibration
which I think, ironically, can help lead to more wear
on
that track at the 'zero flow' position. But it has
also
over the years led to broken exhaust pipes and studs,
problems with the bleeder connector tube in the
coolant
system, broken alternator bracket studs, broken
mount for the auxiliary air regulator, and even a well
tightened air intake boot shaking loose on occasion.
So keeping that idle smooth and your engine as
steady as possible can help avoid plenty of other
highly annoying problems I now think. My engine at
times while idling has looked like it wants to hop out
and run
away on it's own, while I was only considering it's
performance with the vehicle in motion - then the
engine purrs along smooth and still.


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