Is there a test you can do to check the ACTUAL TACH IN THE THE DASH CLUSTER?

Everything else checks out, it has to be the tach itself. I need to know cause I'm planning a junkyard run and have no need to buy another broken tach!

Test continuity?

Thanks.

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Mark
1983 300TD Wagon
Even a broken watch is right twice a day

Did you verify that the module is getting 12V power? Is the clock working?
No continuity test will work, the signal coming to the tach unit is a AC waveform that is amplified by the tach module. Most shops use a known good test cluster for troubleshooting, it would take an electronics tech or engineer and an oscilloscope to repair this kind of thing so a test swap is far quicker therefore cheaper.
I have seen a few bad instruments before, its risky to buy one from a wrecking yard unless they have a return policy in case its bad. The speedo shops charge a lot of $$ to repair or replace them so its almost always a used one that is put in a vehicle.
Also Jason Schoenfeld sells instruments with a guarantee, look him up using the search feature or PM me for contact info.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Mismost,
I have tach problems also- could you give a brief rundown of how you eliminated the other components?

Thanks

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'83 300D Turrrbo 295K miles

I've tested both types of tachs on the bench. The earlier one will move with voltage, the later one requires a square wave to move it. But I have power supplies, an oscilloscope and a function generator on my bench.

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'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

Did you check the 10 amp fuse on top of the tach amplifier behind the passenger side kickpanel, it is an aliminium unit on the right hand side wall, and the fuse is right on top of the aliminuim housing

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'85 300 D Diamond in the rust

Does this apply to 1980 300SD's??? my tach is in-op as well......

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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