Brian,
I do not think the value of the capacitor is that critical. Anything from
ten to twenty five microfarad should work. I believe it is just there to
smooth the output of any noise, spikes, erratic data etc.. The voltage
rating must be higher than fifteen volts.

Ken Lewis
http://neksiwel.20m.com/

----- Original Message -----
From: "Brian Jarvinen" <brianvwagain@YAHOO.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, December 20, 2007 10:54 PM
Subject: [VANAGON] Inside the Air Flow Meter / AFM

> 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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