Discription of electrical items

[Bonymaenjack]

Good evening . I have a fault currently with my Rev counter and ecometer not working (325 1988 ) , I've tested my REV counter which works by connecting a wire from the - side of the coil which also powers up the ecometer .this is not a solution to the problem as I would like it connected as it was originally . I have printed out a copy of the wiring diagrams as per E30 wiki page and following pages 5 and 6 along with the descriptive text page 7 identified the items involved but I really don't know what the following items are or what they look like :
position transmitter item 22
car wire harness connection item 3 4 5
engine plug. item 15
diagnosis connection item 14

If someone could describe a step by step guide on how to physically test the circuit from the coil eventually feeding the blue connector ( black wire ) into the instrument gauge I would be extremely grateful
I have noticed a 3 connection flat female connection hanging just below the drivers side with the following colours yellow/white , green , black with no corresponding connector adjacent
Thanks in advance

[Brianmoooore]

First of all, the rev. counter is NOT powered from the coil, and connecting it this way risks damaging it, since there's no provision in the rev. counter to deal with the voltage spikes from the coil. Rev. counter is driven by a dedicated output pin on the ECU.
If your car has the tree pin plug you describe, I suspect your car is slightly older than you think, and has the wiring arrangements only used for a short time before the full facelift wiring was finalised.
I also suspect that there's something you haven't told us - does this car have its original engine and engine loom?

[Bonymaenjack]

First of all, the rev. counter is NOT powered from the coil, and connecting it this way risks damaging it, since there's no provision in the rev. counter to deal with the voltage spikes from the coil. Rev. counter is driven by a dedicated output pin on the ECU.
If your car has the tree pin plug you describe, I suspect your car is slightly older than you think, and has the wiring arrangements only used for a short time before the full facelift wiring was finalised.
I also suspect that there's something you haven't told us - does this car have its original engine and engine loom?

The full story is the car caught fire within the fuse box area , that and the loom have been replaced 2nd hand purchased from Fritzs bits , the age of the loom is unknown .everything else works except items associated with the rev counter ie 13 button OBC (not all the functions work ie fuel consumption ) I think it's more of the case that the replaced loom is older than the car .I've tried following the wiring diagrams but I'm more competent with mechanical than electrical items and have hit a wall .The diagram shows two black wires from the coil whereas I have one which feeds into the ECU ,my ECU is the motronic 55 pin ending in 173 The ECU or it's harness has not been replaced including up to the diagnostic pin .In the engine bay the loom was cut back and all joints soldered and heat shrunk just before entering the fuse box. so I've tried to keep as a much of the original as possible . As far as I'm aware the engine is the original as I had been using the car prior to the fire with all items operating correctly.
I've found the black signal wire feeding into the gauges and tee'd in but with no success so if you could suggest how to overcome this I would be extremely grateful .I'm loathe to replace the carpet and refit the interior with these items still not working

[Brianmoooore]

Is the three pin plug you describe part of the body looms, or part of the engine loom behind the instruments?

[Bonymaenjack]

Is the three pin plug you describe part of the body looms, or part of the engine loom behind the instruments?

Brian it's part of the loom .the yellow /white and the black wire from the 3 pin plug feed into the blue instrument plug at the back of the clocks , obviously their not being fed from anywhere .the green wire in the 3 pin connector is going back in the loom towards the fuse box.So I'm assuming I need to locate the correct wire and then hard wire them to the yellow /white and the black wire to enable the gauges to work ?

[Brianmoooore]

Sounds like you have the older version of the car loom, and the newer version of the engine loom.
Two ways out of this - either a) convert the car loom to the newer version or b) the engine loom to the old.
a) Remove the three pin plug, insulate the green wire (not required), extend the black and yellow/white across the car, up the duct behind the glovebox into the fuse box, and out into the body side of the C101, where the black goes to pin 9 and the yellow/white to pin 8.
b) If you have the matching three pin plug from the loom you removed, remove it with as much wire attached as possible, unplug the engine ECU, remove the cover from the plug, remove the tape from a section of loom close to the plug, find the black wire from pin 6 and a white/black from pin 32, cut them, and splice the ends that go towards the ECU to the two relevant wires in the three pin plug. The cut ends of the wires that go along the engine loom are abandoned.

[Bonymaenjack]

Brian , I've used option B which has done the trick , a massive thank you , I didn't have the male 3 pin connector plug so I cut it off and soldered the joints and connected as you described .The OBC is still showing PPPPP when trying to set the alarm code , fuel consumption and range but at a least thanks to you I've made small but significant progress.

If I can get the above sorted and the speedo then I can start putting everything back into place .

[Brianmoooore]

The yellow/white is the fuel rate signal, BTW, used by the econometer.
PPPPP on the OBC is its 'fault' code. Disconnecting it from all power, and reconnecting may sort it.