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Speedo and Tacho wiring

Matt Dunn

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I have some questions on wiring the Speedo and Tacho Outputs.

We are using VDO speedo and Tacho Gauges and I am trying to get them to work off Aux Out 1 and Aux Out 3.

Not worried about calibration just yet as I think I have that side of it figured out,

but trying to get the Key On Sweep to work so that I can make sure the wiring is right.

Usually the Aux Outputs switch to earth, so does that mean that I will need some sort of external pull up resistor from ign to the signal wire,

so the ECU can pulse it to ground to create a signal?

At this stage I can not get either gauge to work.

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They have a pull-up to 12V built-in so it should normally work out of the box.  For the speedo is the sweep frequency and sweep time set to non zero and the key on sweep is set to on?  And same for the similar settings in tacho - sweep RPM, sweep time, multiplier and key-on sweep enabled?

Does the speedo say it will work with a square wave signal or is it AC only?

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