I'm doing a trans swap on an '87 190D 2.5 Turbo (from auto trans to 5-speed). After pulling the trans and flexplate, I noticed a sensor located under the starter, that I believe is the tach sender. I couldn't see anything on the auto trans flexplate that would trigger this sensor (other than the teeth on the ring gear).

I also carefully inspected the manual trans flywheel which is going on this engine, and couldn't see anything to trigger this sensor either (other than the teeth).

Is this the tach sender that I'm looking at, and if so, what triggers it?

SteveM.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

1 bump and that's all. I promise.

Steve

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

I don't have any first hand experience with this sensor but I'm pretty sure it's some sort of "hall effect" sensor to provide engine RPM information for the tach, EDS and the KLIMA relay. Some part of the sensor should be mounted very close to the ring gear teeth and I suspect the teeth are used to trigger the sensor. The raw speed signal is fed to the EDS computer which processes it and produces variable frequency two volt AC signal which is then distributed to the various systems that are interested in engine speed data.

I believe its electromagnetic, ie a ferrous moving object induces a current in a coil . does not require physical contact.
Keith