I have this VDO speedometer and I would like to control it with digital signal. I do not want to use hall effect sensor (HES) (or any sensor at all) because I already have car's speed. I would like to send signals to speedometer's pins and have speed displayed. HES connects to 8 and 6 pin, but electronic control (probably from ECU) is only connected to 8. I tried both configurations manually - I connected +12V or GND to it - needle barely moved. I tapped it with constant speed - same result. What would be correct way to control this thing? What digital signal is supposed to come from ECU to this speedometer?

  • So test the original wires that supplied it and evaluate the signal. Did that for a rev counter once and built a driver circuit using a hall effect…
    – Solar Mike
    Aug 26, 2021 at 6:27
  • I do not have original wiring - I bought the speedometer and now I want to use it
    – Voyze
    Aug 26, 2021 at 6:36
  • 1
    Then do some serious research on VDO and their products and find the input signal expected. Good luck.
    – Solar Mike
    Aug 26, 2021 at 6:46
  • I tried supplying PWM to 8 pin - no matter duty cycle, at 490Hz I get 20km/h
    – Voyze
    Aug 26, 2021 at 7:37

1 Answer 1


Found out - speedometer is controlled by frequency. One km/h needs about 25Hz. So at 1000Hz I got 40km/h.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .