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Old 02-04-2012, 01:07 AM
PackerEdgerton PackerEdgerton is offline
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Join Date: Jan 2012
Posts: 450
Differences in Tachs for W123 between 82-84?

Hi guys,

I'm trying to replicate Funola's DIY tach on my 1983 240D with Manual tranny.

DIY tach for 240D w EGR- easy!

I am assuming my 83 has EGR (gotta check that)

Funola used a tach/clock out of a same model year (83) 300D with automatic.

He was able to very simply swap in the tach and run a signal wire from the EGR controller.

I have found a source for either an 82 or an 84 tach.

However, in testing the tachs, here's what he said:

The calibration appears to be quite different between the two model years.

Results:

1982 5000 rpm at ~80 Hz

1984 4500 rpm at ~10 kHz (seems to have different pickup signal vs. 1982)

I suppose that I should simply pick up an oscilloscope and figure out what signal is coming from the EGR controller, but do you guys happen to know which of the tachs I should get?

Thanks much,

PE
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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!
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