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Old 09-21-2008, 02:39 AM
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Join Date: Sep 2008
Posts: 4
Tachometer not working

Hi, the tachometer on my 124 250TD does not work, on turning the ignition ON it deflects and stays at 500 rpm. I tried fitting another used instrument pannel to see where the the problem lies, but it did'nt work either. where is the pickup for the tachometer, is it on the flywheel. could it be a problem with the pick or i am not quiet sure

Could some one please advice.
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Old 09-21-2008, 10:48 AM
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Join Date: Jun 2006
Location: Ft Myers, FL
Posts: 26
Try a seach for the problem.. lots of info here.. On my 300DT it was the over voltage protection relay.

Phillip Babcock
Ft Myers Beach, Florida

2005 E-320 CDI Desert Silver
2005 E-320 CDI White
1992 300D 2.5 Turbo 2 tank WVO system - selling
1984 300TD Wagon 2 tank WVO system Sold
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Old 09-22-2008, 12:41 AM
compress ignite's Avatar
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Join Date: Feb 2004
Location: 32(degrees) North by 81(degrees) West
Posts: 5,554

The Klima relay (Behind the plastic "wall" behind the Battery) will compare the
Tachometer signal with the speed signal from the back of the Air Conditioning
Compressor...and if there is too much difference No A/C.
So...Fixing your Tach signal May give you Air Conditioning again.

The OVP relay is in the same area behind the plastic wall.It's only job is to
protect the expensive "Brain" type components (EDS[engine computer],Cruise
Control,and Air Con CCA) .It will be a silver relay with at least one 10 amp
fuse underneath a red plastic cover on top of the relay.

Looks like this:
Attached Thumbnails
Tachometer not working-screenhunter_05-sep.-22-00.41.gif  
'84 300SD sold
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Old 09-22-2008, 12:31 PM
NY300SD's Avatar
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Join Date: Feb 2007
Location: Westchester, NY
Posts: 133
For me it was the OVP relay. Tach and a/c came back.
"Poor Krusty, he's like a black velvet painting come to life." -Lisa Simpson

1995 E300D 216k black/mushroom

1982 300SD (sold)

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Old 09-23-2008, 11:27 AM
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Join Date: Sep 2008
Posts: 4
I guess the A/C compresser is not orignal or the OE one, it had been changed by the previous owner.
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