jd964t

Hi Fritz, totally understand, thank you very much for trying. It must be in super tight for just the blue cap to come off because my Control Unit came out of the socket reasonably easy but the blue cap took a little bit of effort once out.

If the Control Unit was reasonably priced I’d just replace it but as you say it’s pricey and I’m not convinced it’s the problem if no tach signal is getting to the socket of the Control Unit.

So question remains; why is there a signal at T15 but not at the socket? I’ll put my thinking cap back on!

Many thanks again.

Cheers

Nyx

Might be a long shot but the magnitude of the frequency voltage is unknown unless you use an oscilloscope to measure accurately.


Example
Hz @ 2VDC
VS
Hz @ 12VDC

Try measuring VDC where you are picking up Hz.
might be inductive pickup being read on the multimeter but not enough voltage for the early 90s input to the dash instruments. A long shot but possible?

fritz k.

I think this approach doesn't go any further. Firstly, it is an inductively generated AC voltage and not a DC voltage. And secondly, the decisive signal for speed detection is not the voltage but the frequency or its change and for this we have a "known good" value, namely 45 - 50 Hz at idle.

Fritz