Today I noticed that the needle on the tach does not rise smoothly with the speed, it jumps in 100-300rpm increments but it falls normally when decelerating. Bad tach? Bad sending unit? Something else? Any input is appreciated.

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Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

I am experiencing the same issue with my tachometer - I'm not sure if it is related but my electrical system is totally messed up right now. What is your battery voltage while idling? I think it's ID #24 using your climate control unit.

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Scott C.

2006 E320 CDI (120k miles)
FOR SALE: 1998 E300 Turbo Diesel - Black w/Tan Leather - Euro delivery (236k miles)

I've noticed mine is jerky sometimes at lower rpms. By 12-1500 it rises smoothly. Occurs moreso on colder mornings.

My charging system is good FWIW.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Mine is jerky up to and beyond 3K RPM. Have had no problem with the charging system. I do have a CEL for a bad GP and "engine temp. light error". I wonder if that could have something to do with it.

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Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

On a non-Mercedes that I owned previously (VW) the tach needle would get sluggish in the very cold. You could see where it would bind, so it was obviously the same spots. Once the interior was warmed up to 40 or so, it would work fine.

Today its working fine. I'll keep an eye on it and see what happens.

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Muleears
'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K

I've seen the tach on our '99 act a little jerky occassional, but everything appears fine.

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#dieselFLEET
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'97 E300
'99 E300

I'd suggest a very tiny dab of thin oil would fix that. Whatever the needle rotates on is probably just a little dry.