Russ's 2.1 SED Auto now in Mandarin

[Dieselman]

We shall see. A duff crank sensor normally means a dead rev counter, not one that flickers upwards.

[White Exec]

Think you might end up having to take the dash out, but worth swapping the sensor if you can lay hands on one easily. Does sound like a dodgy (can I say that after yesterday in Parliament?) connection though. Maybe a dry joint on the pcb inside the tacho.

[russ92xmsed]

It has given up before now, the rev counter, but always sprang back to life. This afternoon it was absolutely fine. This morning it flickered about. Typical!
But the blower now only works on full speed. I cant win!
It must be an electrical connection then and inside the car, if a duff sensor causes no rev needle action. ERGH! But where???? Poo!

Don't want to take the whole dash out!

[russ92xmsed]

More plug checking this afternoon. All fine. Checked the earths in the footwells. Well drivers side pristine. Passenger, hasn't got one. Probably never did. Who knows!

I have had a thought, although it's possibly not it. Alternator. Not checked the out put yet, thundering here now. But could it be the voltage regulator dying. I only say this, as I noticed today, the buzz to the electrovalve sort of pulses. Don't remember that being normal. Probably is. Of course the flaw to this idea is only the ignition was on and not the alternator. But power surges might be making the needle fluctuate. But then wouldn't everything else be effected? And they don't appear to be.

This morning the Rev needle was all over the place or dead. At one point driving off from a set of lights. I could have sworn I saw a puff of smoke from the bonnet right above the hydractive connector behind the sphere.
Then got Automatic Suspension message a few times after that. I could have imagined it, and no there wasn't a car in front of me. I checked under the bonnet and nothing. No unusual burning smells and the plug innards were prestine. Wonder if it was WD40 being burnt off? Who knows.

Anyway, the second drive this morning saw it all behave as normal. But blower not working properly only on full, where as when the needle was misbehaving the blower was fine and would work on all settings. Must get to the plugs on the blower and check them. Weather not playing ball today to be able too. I'm sort of thinking the two are almost related. Or at least putting the blower on full blast seems to make the needle flick more. Which of course comes back to possible power feed issue. Hence why I'm thinking Alternator......????

Sorry more thinking aloud.

Still on a totally different note, the LHM tank has stopped sloshing LHM all over itself.

[White Exec]

If the alternator output were fluttering/unstable, you would see it by turning on the overhead interior light, which would flutter with the voltage. EV buzz does pulsate - not an even note.

Think you really will have to explore behind the dash, if blower and tacho behaviour seems to be linked.

I will have a peer at the circuit diagram, if I have it, to look for anything they might have in common.

[russ92xmsed]

I'll do that trick with the interior lights tomorrow.

Thanks for confirming the Ev buzz Chris. Starting to question everything now!

It's only a hunch about the blower and tacho being related. As far as I can see on the wiring diagrams they dot have much in common. It's more likely I expect, overall power feed that is causing something. AHHH I don't know....

Think you're right about the dash. It's almost tempting to take the whole lot out.... Not that I really want too.

[White Exec]

Hi Russ - and John...

Have taken a look at circuit diags for blower and tacho, to see whether they have anything in common (eg immediately shared supplies).
Drawing bit of a blank, partly because I don't have diags earlier than RP6383, which John I'm sure you will have.

On the diags I do have, something annoyingly absent:
Instruments 520-0/10 onwards, and -0/20 onwards...
...all show the tacho, but ONLY connected to its sensor, and NOT to any live supply.
Is this a circuit diagram error?
Common sense would suggest the tacho ought to be powered up by F19, like the other instruments/warnings.

Also, oddly, 520-0/20e shows the tacho as only connected to its sensor by ONE lead. ??

Also note that all diags show tacho input also connected to the diagnostic socket, as follows: (503-00/1 a b c)
B1 Tacho -TDC
B2 Screening/body earth for tacho
B3 Tacho +TDC
This suggests that sensor is polarised, and connecting lead is screened (to chassis).
Presumably all three connections are important.
Also implies that sensor can be checked via the diagnostic socket.

John,
If you have the correct diagrams for Russ's RP5712, this would clear things up, hopefully.

Looking a the blower, again need correct diagrams, and ?? confirmation about which heating/AC control system Russ actually has.
Wonder about the interior temp sensor circuitry, and whether that could be feeding wavering info to (any) temp ECU.
Also see (on all the diags I have), blower is fed by F2 and then feeds the blower/speed control via Relay #821.

On both blower and tacho, wonder whether it could be down to Good Old Ignition Switch poor contact.

Just some thoughts.

[citroenxm]

No you dont want to.. If you see the wires behind there you will shite yourself. And wonder wtf is being powered..

[Dean]

Russ, the Binacle housng comes out easily and since you have a spare car i would be tempted to just remove yours and trial fit the spare one to make sure its not the tach itself or pcb thats the issue.

D

[White Exec]

Lexia on that tacho sensor?

And, when it comes to behind the dash, methodical checking with appropriate circuit diagram is essential. Not something that can be done hit-and-miss; could make things worse!