There is a short cable from the wheel to the box - which is an odometer
- then a longer cable from the box to the speedometer. The purpose of
that odometer is to turn on the O2 light in the instrument pod. The
light would come on every 60,000 miles or 30,000 miles depending on the
model van. It was a warning to change the O2 sensor. The odometer has a
button on top and a detent and can be reset back to zero at each O2
Sensor change, There are speedometer cables out there that are long
enough to bypass the odometer - and many do, just keeping up with the
mileage so as to know about when to change the sensor. Others just run
the thing until the o2 sensor begins giving trouble. I put the longer
cable in mine, last time I had to change out the speedo cable. Works
just fine.

John Rodgers
On 6/17/2012 4:51 AM, ralph meyermann wrote:
> Volkswagen had a box with its own odometer you had to reset every so many
> miles,if I remember right it tripped an O 2 sensor light every 20k or 30k
> mile's, my diesel doesnt have one so I don't know everything about it!!
>
> Velma 82diesel 1.6 na westy
>
> On Jun 17, 2012 1:31 AM, "Glen Moon"<glenmoonfl@hotmail.com>  wrote:
>
> 1981 Westy 122K    speedometer acting weird.  It stayed a zero up until
> maybe 30  then started to work.    Then when I slowed it dropped in steps,
> when fully stopped it read 20  mph.    Later worked OK.   Pulled spare tire
> and found the cable from left front wheel goes to a mid-point junction box
> behind the front bumper and above the spare tire. Then a second cable goes
> on apparently to the speedometer.
> The first cable appears not to original as it is way to long and some one
> looped it in an extra 20 inch diameter loop.  I added some support wires to
> try and make all the curves smooth as one curve seemed very tight.  Hope
> this works.
>   Any way, looking up the replacement cable part, there is one described as
> bye passing the junction box.  What is the function box for and what is the
> best plan for keeping this 1981 going?
>
>   Glen
>