[T3] Speedometer recalibration

Jim Adney jadney at vwtype3.org
Tue Jan 4 07:23:11 PST 2022

On 4 Jan 2022 at 6:33, EL PUERCO wrote:

> Is this even possible? Is there a math function I can use?

There are two different kinds of "recalibration" possible.

If you have switched to smaller tires, for the look, a certified VDO shop may 
be able to rebuild your speedometer with different internal gears, so that 
your odometer measures correctly. This will cost more than you want to pay.

To get the speedometer to read a bit higher or lower requires a special 
machine which changes the strength of an internal magnet. This will 
probably also be needed after a change in the gearset. I do not have one of 
those machines.

For either problem, the error will be a constant %, so you can multiply by 
some factor to get the actual speed.  

It would be extremely unusual for the magnet to change on its own, so if your 
only problem is that the speedo reads wrong, there may be something that is 
hanging up inside the speedo. They are usually sealed pretty well, but is 
your area extremely dusty?

If your needle bounces a lot, that's a different problem. It can be the cable or 
it can be internal to the speedo. If you take the speedo out and try to spin its 
input with a small screwdriver you can tell. It should spin almost completely 
freely. If it has a tight spot or feels stiff at all. I can probably fix it.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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