My tach simply doesnt work. I have searched around and haven't found much information on fixing this. If we can get a list of things to check for any ways to troubleshoot perhaps we can make an informative tachometer troubleshooting thread as well as helping me get mine working!

Is your car a CA model?

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

in 85 ca and fed were identical... so it does not matter.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Here are a few threads to read:

This one has a lot of information on both CA and Fed cars:

1985 300D CA Emissions Tachometer repair

This is a thread on my troubleshooting my 1984 tach problems:

Figured out why my Tach won't work...

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1984 300TD

They are far from identical. The CA has a trap oxidizer and different emissions components including an emissions computer. I used to own one and even have a specific supplement shop manual for the car.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Two things to check......
OVP (overvoltage protection relay), right knee bolster panel under glove box, known to fail after many years. Easy to replace, always keep a spare in glove box.

Tach pickup on bell housing above flexplate. It's magnetic, clean it up.

Alan

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DO IT RIGHT THE FIRST TIME, DON'T BE A HACK
Political Correctness is NOT part of my vocabulary
and finally FIGHT CRIME...SHOOT BACK

'82 240D Stick
'85 300D Auto
Drove my first MB at age 16 1960 300SL W190

Little known fuse hidden behind glove box could be blown.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

I'm pretty sure he is only talking about the tach set up.....

My '85 tach has sat on 0 since I've owned the car. I've replaced the EGR computer, tach pickup, OVP relay. I doubt it's the gauge but I will swap that sometime when I'm around somebody with one.
Good luck with all that......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

can someone post a pic of the overvoltage protection relay on a w123 and its exact location please.

Did you see this thread ?
http://www.peachparts.com/shopforum/showthread.php?t=138818