The other day my tach came alive for a second or two and died again. The first time, it bounced a bit and died again. The second time, it held up at 2000 RPM and then died. I think both times the tach came alive I might have had the right turn blinker on.

Should this give me some idea of what is going on?

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1983 300 Turbo-"Nora"
1983 240D Auto "Lucia"-slowest on earth-1st love
1985 300 Turbo-Blue Goose-slowly plucking parts

http://i117.photobucket.com/albums/o...ly15/mbsig.jpg

1.The "Advanced Search" is your friend.
2.You haven't done any Diagnosis.
(I.E. Testing with Multimeter,studying Schematics,Etc,)
3.You want me (Or some real Expert) to comment on a turn signal [Maybe?]
Re Activating a Dead Tachometer?
4. For your preferred method of automobile fault diagnoses,try:
California Psychics ® 1.800.573.4784

Assigned Reading Materiel from the Archives "Advanced Search Function":
http://www.peachparts.com/shopforum/search.php?searchid=4248399

This one post MAY help you more than all the others:
http://www.peachparts.com/shopforum/showthread.php?t=207837&highlight=tach+amp

EDIT: On Reading sd300td's reply ,I Like it!

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'84 300SD sold
124.128

^ Heh...

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1989 300E 144K

just a guess. Bad ground.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)

Bad ground? Meh, its usually the tach amp.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

Absolutely!

MB has infamously tied the tachometer circuit to the turn signals. The turn signals use a mixture of oscillating frequencies of different amplitudes to create the classic "on/off" of the turn signals. The right turn signal uses reverse polarity frequencies from the left turn signal. The fact that the tach works with the right turn signal means that the tach signal is being negated by the left turn signal.

Does the tach work if you turn left even with the right turn signal on? If so, you can add a SPDT switch to your dash that will solve your tach issue. Take the wires that go to your turn signal relay and wire the new switch so that the common is fed by the right turn signal, and the two throws go to the right and left turn lights. Leave the right turn signal on all the time so the tach works, and when you want to turn right or left then you just use the new switch to route the signal to the correct side. When the steering wheel returns to center you'll lose the tach (cuz the turn signal will turn off) but that should break eventually.

Good luck and let me know if this helps!

BTW, there's no reason why the tach would be affected by your turn signal. Search the forum for "cigarette butt" and that should lead you down the correct path. My apologies if this seemed snarky, it's not meant to be. I just couldn't resist.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

I was waiting for blinker fluid to thrown in somewhere.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

'Other than captive Electrons seeking an outlet? No.

The Big Brother to PART of your Dilemma is named "LIGHTNING"
(Overcharged electrical source seeking Ground)

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'84 300SD sold
124.128