Hey guys, I dont have any local OM617 guys that I know well enough to bring my DMM over and play, but here is what I need to bring my devious 240D factory tach desires to fruition...

What is the signal voltage coming off of a stock OM617.95x rpm sensor (tdc sensor ?). I think all you have to do is set your voltmeter to "really small" (or autorange), start the motor, unplug the tdc sensor from the bottom of the tach amp, and take voltages from pin to pin. One pin is a shield, and the other two pins should be a colored wire (yellow and brown ?).

Once I know this voltage, I can compare it to the voltage on my 240D's rpm sensor (for the EGR system...) and decide what (if anything) needs to happen to that signal before sending it into an OM617 Tach amp and into a 300D tachometer (which will nicely fit in the place of my clock =)

Any help is appreciated. I couldnt find this in the ETM. I plan on posting the results in the "240D tachometer" thread for archival purposes.
-John

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2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

Im a local OM617 guy that would love to visit with another forum member and see another MB diesel.

Does your tach work ?

shoot me a PM...school is busy for me right now, but I'd like to see...

-John

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2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

Mine doesn't work, and I have replaced everything short of the crank sensor...

I even got a new gauge pod (a tested working one from **************) and a brand new amplifier, voltage at the pins in the dash to the tach is 13.7 at idle...but tach still doesn't work. I suspect the sensor on the crankshaft....am I right? It'd just mean there's no "pulse" in the signal for the tach to read....

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

See, thats the thing. If someone (maybe me and Sady...) could measure that output on your sender, I could post that up and then you could compare - that would be a (relatively) definitive go-nogo test for your sender.

Other than that, us cheapo MB dieselers isolate the cheapest parts first, then the expecsive parts are checked last =)

-John

__________________
2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

somewhere the gods of EE are laughing at me...

So I go out to my car and put my DMM on the crank sender. The multimeter reads to .001v (I know it it not that accurate though...) this means "no readable voltage", if you short the leads you get .001v reading, if you just let the leads fly you get .004 - .012v). No AC or readable frequency (It reads freq also...)
So I go to the .pdf's and the ETM and pull the EGR computer. with the computer plugged in, engine running, ground on pin 3, signal on pin 4, 12 on pin 2. it has ground and 12, and approx 2.5vdc on pin 4 but still no AC on pin 4 and no readable frequency.
I'm guessing that I need an O-scope. My guard base has one I can drive up and use, but I need the time to get up there... this also means my OM617 contact would need to get an oscope also...

-John

__________________
2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

The sensor is either a hall effect, capacitive or a coil. With any of these, you are looking for a pulse or sloppy square wave rather than a rpm dependant voltage.
If you can get ahold of an automotive DVM, it should have a duty cycle setting that will at least tell you if the sensor is working.
On the O'scope, it will probably look like the top half of a sine wave with steep sides.
It almost sounds like your sensor is bad, I'd expect either 0 or B+ with power to the sensor but engine not turning. With 2.5VDC, I wonder if the output has fried.

Michael
Sorry, no diesels in my household.

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120