Using A Timewise 797A With A VDO Speedometer Cable Sensor

When I recently competed in the Baden Classic rally with Harald von Langsdorff we used a Timewise 797A rally computer that Harald had recently purchased.  After the purchase Harald had the Timewise 797A sent directly to me.  I was pleased to be able to do some bench testing in my basement to check that the Timewise 797A was working properly.  It also gave me the opportunity to re-acquaint myself with this rally computer.  The last time that I had used this rally computer was with Mark Everett in a SCCA Finger Lakes winter rally.


Our Rally Set-Up For The 2014 Baden Classic

For the Baden Classic the full capabilities of the Timewise 797A were not needed but it was useful to have such capabilities on hand.  Also by taking the rally computer to Germany where it was left it will be available to Harald for other events in Europe.

I was somewhat concerned that the Timewise 797A might not work with the VDO Speedometer Cable Sensor that Harald had previously installed in his 1958 Mercedes-Benz 220S Cabriolet.  Last year we successfully used a Brantz Retrotrip with this cable sensor, so we had some previous good experience with this sensor.

VDO Speedometer Cable Sensor

VDO Speedometer Cable Sensor

Before leaving for Germany, I contacted Jack Christensen of Timewise and outlined my suggested connection strategy.  As far as we know, no one had used this type of sensor with a Timewise rally computer before.  Jack thought that the connection strategy would be fine and he also provided me with an alternative wiring strategy in case our first strategy did not work.  As it turned out, our initial wiring strategy was completely successful.  The connections between the Timewise 797A and the VDO cable sensor that worked for us are as follows:

  • VDO Sensor positive power wire (Black) to Timewise Pin 2
  • VDO Sensor negative power wire (Brown) to Timewise Pin 7
  • VDO Sensor signal wire (Blue) to Timewise Pin 4

I hope that this information is useful for anyone who wants to use a Timewise rally computer with a speedometer cable sensor.

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