Lazy Tachometer?

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PhoenixOp
Posts: 152
Joined: Mon Aug 17, 2015 11:19 pm
Location: Kuna, Idaho, USA

Lazy Tachometer?

Post by PhoenixOp »

Gentlemen;

My 1985 E24 (12/4/1984 production) 5 speed, ECE 635CSi, has developed a lazy tachometer. Most of the time it does not work, other times, it seems to come out of it's slumber struggling to start reading RPM's as it should. It almost acts like a bad connection somewhere. :cry:

After staring at the wiring diagrams until my eyes crossed, I can't find a logical place for said bad connection. The wiring seems to come from the motronic control unit straight to the cluster.

I'm hoping someone has had a similar problem and knows what to do with this. I believe there is an engine speed sensor on the transmission (of all places), but because my car is a manual-euro spec, I'm not sure the wiring diagrams I have necessarily apply.

Any and all ideas or suggestions are most certainly welcome.
Mike Drives: :D
BMW's...
1980 633CSiA
1985 635CSi (EC)
1985 635CSiA
Plus:
1 - E31
2 - E32
1 - E34
3 - E38
3 - E39

Also:
67 Buick Rivera
99 Mercedes Benz SL600
02 Mercedes Benz SL500
07 Mercedes Benz CL600
14 Dodge Dart Rallye XT
15 Ram 3500
User avatar
PhoenixOp
Posts: 152
Joined: Mon Aug 17, 2015 11:19 pm
Location: Kuna, Idaho, USA

Re: Lazy Tachometer?

Post by PhoenixOp »

Thank you for the prompt response.

I completely forgot about the SI board and all it's weird problems. I installed a ProGrama replacement board that did not require batteries in my U.S. Spec E24. Looks like I may have to do the same with this one.

Again, thank you,
Mike
Mike Drives: :D
BMW's...
1980 633CSiA
1985 635CSi (EC)
1985 635CSiA
Plus:
1 - E31
2 - E32
1 - E34
3 - E38
3 - E39

Also:
67 Buick Rivera
99 Mercedes Benz SL600
02 Mercedes Benz SL500
07 Mercedes Benz CL600
14 Dodge Dart Rallye XT
15 Ram 3500
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