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New tach amp found!

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So I found and bought a new reproduction microcontroller based tach amp. It does the sweep and also gives led troubleshooting codes. I am quite excited to try it, however my crank sensor has a slot going though it so it's toast.

Once I get a new sensor I will update on this thread and give you my experiences.

The sensor is a bit tough to get out if you don’t know the trick. I’ve removed them on my w123 and w126. I come in with long (like 12” or 16”) of 1/4” drive extensions to the 8mm nut from the power steering pump side and under the vacuum pump. A wobble head or u joint can help depending on the car - somehow my 85 w123 is different than my 82 w126.

I am the designer of this device.  My email is printed on the bottom of the board if you ever need any support.  And of course you can reach me here.

How cool is that?!

What engine is this for? M110?

It’s compatible with the OM617A turbodiesel. Uses the crank sensor on the front of the engine.  I developed it on my W126 and W123 but it will work on a 1979-80 W116 300SD.

The gassers have different electronics in the gauge cluster.  Luckily they don’t have the same age related issues as the turbodiesel.

W123wrench, question for you...

The tach in m 84 300TD works, but past a certain RPM it seems to work backwards.  Idle RPM seems accurate, then it will go up till about 2000RPM, but then it will start going back down.  THen when the transmission upshifts, it actually jumps up to higher RPM (backwards operation).  I also notice that my front crankshaft sensor is disconnected. 
Does the W123 300TD have a different input for the tach?  My 1980 300SD has that sensor coming straight up into the tach amp.


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