I have a 83 300D turbo w/138K miles and the tachometer has been intermittent, mostly inoperative. I just removed the instrument cluster to repair ( sucessfully) the odometer. The tach was not operating before and now it is just now and then for no reason.
The electrical connections were tight before and are tight now after reinstallation of cluster.

Where does it recieve its signal, and What should I look for next...
Also, would this "loss" of signal have anything to do with my inoperative cruise control. I have pulled the silver box CB out from over drivers left knee and resoldered some suspect connections, but have not reinstalled same.

Please help. And again Thanks to All.

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Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW

There is a pick-up at the front of the crankshaft..that goes to the tach amplifier..the amplifier processes that signal & sends it to the tach.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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And the amplifier is the little upside-down trash-can looking thing right next to the glow plug circuit, on the drivers side fender. This is most likely your problem. Do a search for tach amp (cigarette butt), and you will find several temporary fixes for this over-priced part.

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1989 300E 144K

Agree with MattB, I just went ahead and got a new over priced one. I've got a video of repair, too tedious for me. Don't think it has anything to do with cruise control.

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83 SD

84 CD

Try this:
DIY Tach Sensor Repair
You might still be able to get some life out of your tach sensor, which is usually the culprit for funny tach problems.

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I had the same problem with my 85 300d. I replaced the overload protection relay (it has a fuse in it that may have gone bad). On my car the relay is located by the passenger-side a/c outlet: slide out the glove compartment and on the right wall by the a/c outlet hose is a rectangular bow (finger-size), the fuse is visible. the box lifts out. After replacing the fuse it still did not work , so I bought an overload protection relay from ebay, $15.00, and a new fuse and the tach finally worked after replacing the amplifer or trashcan and pickup line. Good Luck Bryan

An 85 is a different animal. An 83 does not have an OVP relay.

As someone has already stated, the cigarrette filter trick will probably get the tach working for a little while. If it helps at all, it proves that the amplifier is the problem.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

On my '82, it turned out to be the base into which the tach amp (trashcan) mounts.

Read about it here -- Hmmm, tach amp indeed

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1998 E300 +310,000K
1996 E300 +460,000K

Recieved a replacement tach amplifier, installed and the tach is operating great.
Thanks all,

Now I need a parts car.....

__________________
Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW

Good to hear you're operating.

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83 SD

84 CD

Thanks and do not tell my wife I am looking for a parts car, I will end up with another project car to get on the highway....

So what is the 300D you have for sale look like ???

__________________
Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW