techguy512 has produced a tach amp replacement that uses a small microcontroller (computer) to do what the old analog part did. It may be that he can adapt that to convert the signals. The issue is that the tachometer expects a steady stream of pulses, and not bursts - so his algorithm would have to be somewhat complex. It would have to behave like a Phase Locked Loop.

It will be much, much, much easier (not to mention cheaper) to retrofit a diesel tachometer. It looks to be a straight conversion with no extra holes. Some rewiring is required, of course.

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1984 300TD

Maybe not so much. First thoughts would be to go to the next controller in the series. 2k of code space, and two independent timer/counters. One to measure input pulse rate and one to create output pulses.

We would need to know with a great deal of certainty lots of details about the gasser tach (input pulse rate, input signal levels, etc, etc).

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Bob
'82 300D Petrol B-G Metallic

Did the w115/w114 diesels have tachs? I was under the impression that a tach was never offered as an option for that body style which uses a similar gauge cluster as the w108/w109s

I removed the tach from the cluster; it has the following on it:

12V / 24000 Imp.

230 / 29 / 3

8Zyl. / 4Tkt

There is a blue stamp on the unit that reads:

225
10.68

This particular tach unit was used on the m100 engine.

Hope that helps; I greatly appreciate everyones help so far, thanks.