During my trip to Germany to participate in the 2013 Baden Classic car rally, Harald von Langsdorff, the owner of the 1958 Mercedes-Benz that we used in the rally had purchased and installed a VDO speedometer cable sensor. This sensor connects to the speedometer cable and converts the rotation of the speedometer cable into a useable pulse signal. An example of this speedometer cable sensor is shown below.
VDO Speedometer Cable Sensor
Last year during the same event, we noted that the wheel sensor was not providing a reliable signal to the rally odometer. It was thought that the speedometer would provide a more reliable and accurate signal to the odometer. We had a very difficult time finding the proper wiring connection details to connect this speedometer cable sensor to a rally odometer.
VDO Speedometer Cable Sensor
The VDO speedometer cable sensor has three wires coming out of the unit:
The actual functions of each of these wires is not absolutely clear to me, therefore I will not include my thoughts on the function of each wire and for the purposes of this post I will just focus on making the proper connections between this speedometer cable sensor and the Brantz Retrotrip odometer.
The Brantz Retrotrip odometer is an electro-mechanical odometer that is accepted in classic rallies which frequently restrict the type of odometer or rally computer that can be used. The Brantz Retrotrip odometer uses an electronic pulse signal that advances a mechanical counter. Pure mechanical odometers, such as the Halda Twinmaster, have become so expensive and hard to get that organizers will except electro-mechanical odometers as a substitute in most classic car rallies.
Brantz Retrotrip Odometer
My Brantz Retrotrip odometer is shown above. As can be seen it has two distance displays. Below the each display is a push button that will re-zero each display. The toggle switch on the bottom left of the unit is the on/off switch. Also on the bottom, there are the calibration switches to convert the pulses to the proper distance in the displays.
On the right side of the bottom are two cables – one black covered cable and one grey covered cable. The black covered cable contains the two power wires. Inside the grey sensor cable to the Brantz Retrotrip are three wires with the following colors:
The image below shows the three sensor wires that are within the grey cable on the left side. Note that there is some residual on the wires from some black electrical tape that I used to tidy up the wiring.
Three Retrotrip Sensor Wires Shown On The Left Side
The following are the proper connections between the VDO Sensor and the Brantz Retrotrip odometer:
VDO Sensor Retrotrip Odometer
Blue connects to Blue
Brown connects to Green/Yellow
Black connects to Brown
The wiring for other newer Brantz Retrotrip odometers might be different.
Hopefully this post will be useful for those installing this combination of speedometer cable sensor and Brantz Retrotrip odometer.