if your goal is an inexpensive basic analogue volt meter..
they can be as low at $ 4.95 or even $ 3.95 at Harbor Freight ..and in
Oregon ..no sales tax either.
or...
like 15 bucks will go a long way toward getting one that's decent enough.

On 7/3/2014 1:56 PM, Rocket J Squirrel wrote:
> David's suggestion to use an analog voltmeter is a good one. Analog
> meters catch glitches and dropouts that digital meters don't.
>
> The question is -- who has a good value in an analog multimeter these
> days? Simpsons were my go-tos in Ye Days of Olde when Knights Were Bold
> and I had a budget.
>
> --
> Jack "Rocket j Squirrel" Elliott
> 1984 Westfalia, auto trans,
> Bend, Ore.
>
> On 07/03/2014 04:12 PM, Harold Teer wrote:
>> David,
>>
>> Thanks for a great and detailed explanation on the AFM that even I
>> understand.  Between the information from you, Karl, and Neil, this
>> thread
>> will be a wonderful resource in the archives for understanding the AFM
>> better.
>>
>> Have a great weekend and 4th of July,
>>
>> Harold
>>
>> Harold Teer
>> 1991 Westy -- VANGAUX
>> Harrisonburg, VA
>>
>>
>>
>> On Thu, Jul 3, 2014 at 5:08 PM, David Beierl <dbeierl@attglobal.net>
>> wrote:
>>
>>> At 09:10 AM 7/3/2014, Harold Teer wrote:
>>>
>>>> Thanks, this makes sense in theory. Â Can you walk me through how
>>>> to do
>>>> this without the AFM connected if I don't have any fancy equipment.
>>>> Â Do
>>>> have analog and digital meters so have that part covered.
>>>>
>>>
>>> To do it with the AFM in the van, follow the procedure in tencentlife's
>>> video.  Pull the boot off the connector, stick your meter probes in
>>> as he
>>> shows, turn on the ignition and follow his procedure of very slowly
>>> pushing
>>> the AFM vane open with a stick of some sort.  You have to be slow
>>> enough
>>> that the meter has time to respond to any dropouts.  Notice he's
>>> using a
>>> fairly small meter with a fairly quick-responding needle.  If you
>>> have a
>>> larger one that responds very slowly (like a couple of Radio Shack
>>> meters I
>>> have) you have to move the vane slow enough that you can see the needle
>>> dip.  Any dip at all means a problem at that point on the track, you
>>> don't
>>> have to wait for it to fall to zero; you should see the voltage only
>>> rising
>>> as you push the vane open.
>>>
>>> To do it using dry cells or a power supply (and having been reminded by
>>> Neil's photo of the resistor plate itself, I expect a nine-volt square
>>> battery would be fine and maybe easier to hook up to), hook up the
>>> battery
>>> to the same pins the ECU would use.  I don't have access to a
>>> Bentley right
>>> now but according to the video the AFM pins for the waterboxers are:
>>>
>>> 1 - Temp I hot
>>> 2 - AFM wiper
>>> 3 - AFM + supply
>>> 4 - System ground for both AFM and Temp I
>>>
>>> So you'd hook B+ to pin 3 and B- to pin 4.  You'd hook meter + to pin 2
>>> and meter - to pin 4.
>>>
>>> Don't use your digital meter, it will only cause you grief. It probably
>>> only takes 2-3 readings per second, and the reading is averaged over
>>> the
>>> sampling time which is less than half of the half- or third-second
>>> cycle
>>> time.  If your meter has a quick-responding bar graph display you might
>>> manage; but the analog meter responds in real time and is always
>>> reading
>>> the line.  Even if the needle response is slow it will be easier to
>>> deal
>>> with than the digital (may or may not be easier than the bar graph
>>> display.
>>>
>>> If for some reason you do use the digital, set it on a fixed range,
>>> as you
>>> don't want it switching ranges while you're testing.
>>>
>>> Set your meter range as low as practical that's at least half the input
>>> voltage.  As tcl says that will cover the part of the AFM track that
>>> gets
>>> the wear.
>>>
>>> FYI, if you look at Neil's photo of an uninistalled resistor plate:
>>> https://lh6.googleusercontent.com/-c5axVMck2Ks/T-tDy8qL_MI/
>>> AAAAAAAAF2o/Cly2OSeHmUk/s912/AFM%2520Board%2520Wear.jpg
>>>
>>> At the bottom there's the Bourns name and Bosch symbol, indicating a
>>> proprietary part made for Bosch.  8712 means it was made in week 12 of
>>> 1987.  The two crosses and two triangles I imagine are registration
>>> test
>>> marks for the several layers of stuff that get printed onto the ceramic
>>> substrate.  The spot on the left-hand triangle may be an inspector's
>>> mark.
>>>   The long number is Bourns' part number for the plate, the 1
>>> probably means
>>> revision 1 of the device, and the reversed C looks like a test
>>> resistor to
>>> validate the resistor printing process for quality control
>>>
>>> Above that is the wiper track. The right side is the ground side and
>>> the
>>> left side is hot, corresponding to the rotation of the vane in the AFM.
>>>
>>> Now look at the very top.  The two bright dots are where the spring
>>> contacts have burnished the silver paint that forms the conductors.
>>>   Theleft one is + and the right one -.  Following them, you'll see
>>> that
>>> each connects to a green patch with lines on it.  Those are
>>> resistors, and
>>> the lines are where the trimming laser burned away parts of the
>>> resistor to
>>> increase its resistance to the correct value.
>>>
>>>  From the other end of the resistor conductors go to the two ends of
>>> the
>>> wiper track.  If they were the only connections you'd be able to do
>>> this
>>> test with an analog ohmmeter instead of a voltmeter.  But as you can
>>> see
>>> there is also a resistor that stretches the entire length of the track,
>>> with nine connections into the track and laser trims between each
>>> pair of
>>> connections.  That's what's driving your ohmmeter nuts.  It's a voltage
>>> divider that's feeding an offset voltage into the track at those nine
>>> points to adjust the wiper response.  When Bourns builds the plate the
>>> laser trimmer has point contacts that leave the tiny bright mark on the
>>> little side tabs coming away from the various resistors, and it
>>> trims the
>>> resistors in a particular sequence until all the values are
>>> correct.  It
>>> looks as though it does a roughing pass and then a finishing pass to
>>> take
>>> care of interaction between the voltage divider and the two main input
>>> resistors.  Then they ship it to Bosch who glue it onto the metal
>>> mounting
>>> plate.
>>>
>>> While I'm on the subject, in tcl's video the long copper arm is carries
>>> the contact from the AFM connector to the wiper.  It has a carbon
>>> button in
>>> the round end ant there's a flat spring with a bump on it that comes up
>>> from the vane/wiper assembly and presses on it.  However apparently
>>> there
>>> were difficulties with this, because by at least late '83 Bosch had
>>> added a
>>> braided copper flex cable to bypass this button and make a solid
>>> connection.
>>>
>>> Yours,
>>> David
>>>
>