I can tell you how the factory did it - assuming it's electromechanical and
not electronic.

The speedometer magnet was pre-magnetized then it was was put into machine
and tested at speed while the machine bumped the magnet strength down until
it was calibrated.

Tom

From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
Scott Daniel - Turbovans
Sent: Thursday, April 21, 2011 6:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Anyone know how to calibrate the speedo?

fwiw,
I just had a vanagon speedometer in an instrument shop for odometer repair
and calibration ..
cost about $ 100, not 300 to 500.
  such a price would be way high..
125 to 160ish is about right for rebuilding one of these speedometers.

I sorta thought there might be a screw on the back of a vanagon speedometer
for calibration ...and  I just looked an 85mph speedo out of an 84 vanagon
....didn't see any adjustment there, but they are calibratable.

it's normal for them to read a bit high of course.
----- Original Message -----
From: "Mike" <mbucchino@CHARTER.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, April 21, 2011 3:37 PM
Subject: Anyone know how to calibrate the speedo?

>  I took apart a broken Rabbit speedometer to check out how to access to
> the
> speed indicator cup and drive magnet for the speedometer function.
> I found that the magnet can be slid fore and aft on the cable drive shaft
> to
> bring the magnet deeper into/ farther out of the steel cup.
> This would vary the eddy current effect, which would allow one to
> calibrate
> the indication on the needle.  A shop that's capable would charge $300 -
> $500 to do this for you.
>  Mine now indicates 62 MPH when I'm travelling @ 65 MPH (checked by GPS),
> so If I rely solely on the speedo, I could get a speeding ticket when I
> set
> my cruise at 65.
> I'm actually travelling 3 or 4 mph faster than my needle indication, and
> this really bugs me.
> I am aware of the designed-in inaccuracy of the older VW speedos.
> My wheels are stock steel with tires that are stock-sized Michelin Agilis
> load C's all around.
> I've searched for info for this specific procedure. but to no avail.  I'd
> like to take my Vanagon Speedo apart to see if it's similar to the Rabbit
> one in this area.
> Does anyone know if I have to disassemble and re-assemble to speedo many
> times in trial and error method, or is there a way to mock it all up on
> the
> bench and get it done that way?
> If I figure it it all out, I'll post it to the list.
>
> Appreciate any help!
> Mike B.
>

  _____

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