Another problem with rev counter!

[fazzybear]

Ive just discovered another electrical fault with my new purchase 325i se 1991. Everything on the instrument cluster works apart from the rev counter/mpg

I have checked the fuses and they are fine, servive indicator still lights up??

[Brianmoooore]

Rev. counter signal is sensitive to a poor connection where it passes through the C101 engine loom to body connector. (Black wire.) Check that the C101 is screwed together properly, with the lock ring fully home.
If everything is OK there, then the SI board batteries are the main suspect, even if the SI system works. Take the SI board out, stick it in the freezer for half an hour, then measure the voltage across each battery.

[fazzybear]

Will have a look today thanks

[fazzybear]

Checked c101 and all wiring looks ok engine side??

[rovmiester]

I have an 1989 318 with m50 in that has the same problem. Hasnt worked since I have had the car!

[Brianmoooore]

I suppose I can't assume that the OP's tacho. has ever worked since anything may have been done to it, before he bought it.
Check that there is a white coding plug pushed into the lower right front corner of the cluster.
Check for continuity between pin 7 of the blue connector to the cluster from pin 47 of the ECU on the M50, and pin 6 of the ECU on the M20. The wire is plain black in both cases.

[fazzybear]

Brianmooooore i have only just taken ownership of this car so no it hasnt worked for me, all the rest of the instrument cluster works apart from the rev/mpg gauge.

Checked all fuses and no joy, clocks are original along with the engine etc etc. Service indicator works fine. There is no life in the rev counter whatsoever......

[Brianmoooore]

Check that there is a white coding plug pushed into the lower right front corner of the cluster.
Check for continuity between pin 7 of the blue connector to the cluster from pin 47 of the ECU on the M50, and pin 6 of the ECU on the M20. The wire is plain black in both cases.

[fazzybear]

Ok will have a look, can you see the coding plug without pulling the cluster out?

[milescook]

Feel behind the bottom of the clocks, on the left and right of the clocks (inline with the headlight switches) you should feel two knobly "dials" - these unscrew and you can take off the slightly rectangular plastic panel underneath the clocks. Voila, coding plug revealed on the right.

(From memory... )

[fazzybear]

Havent had time to check coding plug but i will later today, i dont know if it helps but the service light has been reset recently and the obc has also stopped????