Rev Counter Of S3

[rogerem]

I have an S3 and the rev counter is showing double the real RPM. Does sombody know why is taht and how to fix it? the rev counter seems original but I don't know now.
How is the rev counter driven by the coils or mechanically?

i would appreciate any help on that matter :unsure:

[david.g.chapman]

I have the same problem with my 1970 +2, but only when the car is really hot in summer.

It could be an electronic trigger threshold that is has drifted as a result of aging in the components. The tacho then triggers on another of the mess of pulses that gets thown at it.

The first thing I would do is check all the resistor values in the tacho and replace any that have changed from the band code values on the resistor bodies. Only try this is you feel competent to do so.

Dave Chapman.