I am interested on installing a tach on my 1984 300TD (Euro-version). It originally had a clock (where the tacho/clock should be) BUT there is already an exisiting magnet or pick-up sensor front center pulley (just like a 1984 US-version would have) to read engine revolutions -considering there was no tach originally- and it also has the short "drum/canister" sending-unit thingy (on the correct mounting bracket) already on the driver fenderwall w/ a wiring harness connecting to the thick main wiring harness which goes thru the firewall. Now what do I have to do in order to hook up a tacho/clock correctly? I have that computer box "thingy" also located in front-passenger right footpanel behind a removable square panel. Please help. I can send you photos if you wish. My car's photo is at www.w123.us It's the one owned by The Benz Bar (me)... send your car's pics at the site, and I'll post them.... Thanks for any advice.

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On the W116 it is a simple 2 wire hook up to the tach. My son has a 1985 euro 300d NA that we are supposed to pull the cluster on next weekend to up grade from the lights to red led's it already has a tach installed That is most likely to be as close to a match to your car as were likely to find I already intended to do a photo how too write up I will make a note of the wires color codes and where they run too then PM me if you have not figured it out by then and I will shoot it right off to you. Also some one just posted a german w123 site that is in german but you can connect thru a translation program the translations are poor but you might find a schematic there the link is here but it is very slow but I was able to get some great information on our euro cars. http://www.online-translator.com/url/tran_url.asp?lang=de&direction=ge&template=General&cp1=NO&cp2=NO&autotranslate=on&transliterate=on&url=http%3A%2F%2Fwww.thomconsulting.de%2FMB%2Fw115.htm
Again it does work it is just SLOOOOW
Dave S

The german site has a section on adding a tach but it might help if you know some one who reads german the translation can be pretty bad but it is there.
DHS

I read/viewed thru that slloooww German site, and it was actually quite comprehensive BUT not much help in adding a "diesel" tach - they focused more on a "petrol" tach upgrade.... If any tech or experienced MB-guru has insights or knowledge, please kindly post your advise. The German site did indicate that the newer '83-'85 TDT models were already "pre-equipped" with the pulley sensor and harness...like mine is. So I guesss all I have to do is find/install the correct wiring and routing for the tacho/clock to work in conjunction with the sending unit already present on the car?... Remember, I have a '84 300TD (euro) so I do not have that tall drum/canister tach sending unit on my fender - instead it is the shorter version. Thanks in advance for all/any input....

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My Mercedes-Benz Homepage and W123 Owners Photo Gallery and W111/W112 Coupes & Convs Gallery
2005 Northeast GTG and 2005 Mid-Atlantic GTG and Summer '09 Central FL GTG on YouTube

Speaking of the tach amplifier why is it the short ones have nothing plugged into them if you take the cap off my gas s class has the short canister but there is nothing plugged into the short socket and I have never seen one in the junkyard any one know? Sorry the German site could not answer your question I only looked at it briefly because I did not want to die of old age waiting for pages to load. But it is great if you own euro cars we have 2 and the site is real good about giving part #
DHS