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Speedo signal lost

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monoi
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Speedo signal lost

Post by monoi » Sat Jan 13, 2018 12:57 pm

Hi there,

I just removed and refitted the auto box valve body to solve the harsh shifting which occurred at times, as described in other posts. I didn't find any filters, clogged or otherwise, only some grey gunk where the magnets are. So much so that I took it to a specialist to have a proper look and take it apart. He changed the pressure regulator but aside from that, nothing was amiss. Not cheap though...

Anyhow, I managed to refit everything and the shifting is a lot smoother now so there is that. However, the speedometer is not moving anymore. There was a grey tube in the box which is probably the speed sensor, although I thought the latter was on the rear differential.

Would that be the culprit? Any reason why the speedo would just stop working?

You can see the connection protruding on the picture:
http://s33.photobucket.com/user/monoi2/ ... t.jpg.html

Pascal
635 Csi highline 3/89

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hornhospital
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Re: Speedo signal lost

Post by hornhospital » Sat Jan 13, 2018 4:47 pm

Nope. Transmission has nothing to do with the speedometer reading in a late model E24. It's read from the differential sensor.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"

monoi
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Re: Speedo signal lost

Post by monoi » Sat Jan 13, 2018 4:59 pm

That's what I thought.

The weird thing is that I didn't go anywhere near that sensor. Could I have disturbed the wiring?
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sharkfan
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Re: Speedo signal lost

Post by sharkfan » Sat Jan 13, 2018 5:11 pm

Speedo sensor wiring goes down the inside of the rhd drivers sill under the carpet, under the rear right hand seat and out from under the right hand seat along with the fuel pump wiring.
2001 Alpina B10 V8 Touring (1 of 12 rhd)
1997 Alpina B12 5.7 L (1 of 2 rhd)
1995 Alpina B10 4.6 Touring (1 of 1 rhd)
1985 BMW M635CSi (1 of 524 rhd)
1982 BMW 635CSiA (1 of 100's left from the 1000's made and still valiantly fighting against a rusty grave)

monoi
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Re: Speedo signal lost

Post by monoi » Sat Jan 13, 2018 6:01 pm

So nowhere near when I fiddled.

In the spirit of it must be something I did, the other thing I did was to remove the cam cover to change its gasket. So I removed the air box, MAF and the rubber hoses. I also disconnected the plugs to the MAF and idle sensor (I think that's what it is called). I was left with another connector, splitting off the MAF wiring loom, when refitting but I didn't think it was connected to anything and now I'm not so sure.

http://s33.photobucket.com/user/monoi2/ ... w.jpg.html

Does that 3rd connector go somewhere? Would that have an effect on the speedo?
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raykoke
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Re: Speedo signal lost

Post by raykoke » Sat Jan 13, 2018 6:59 pm

Is your OBC still getting the MPH signal?

Good luck,
'85 ///M635

monoi
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Re: Speedo signal lost

Post by monoi » Tue Jan 16, 2018 3:44 pm

OBC is working as its supposed to, except it doesn't get mileage so range or fuel consumption are wrong obviously. A total mistery why I should lose that signal, although it's obviously something I did.
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raykoke
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Re: Speedo signal lost

Post by raykoke » Tue Jan 16, 2018 11:21 pm

I had a broken track on the cluster PC board that caused what I believe are the same symptoms.

I didn't do anything to encourage it happening (either!).

Good luck,

Ray
'85 ///M635

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603racing
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Re: Speedo signal lost

Post by 603racing » Wed Jan 17, 2018 12:43 pm

I put a rebuilt cluster in my car one time, the speedo went wonky then quit about 50 miles later. I was sure it was the cluster but I swapped out the sensor in the diff with a spare I had as a quick alternative to pulling the cluster, the sensor swap fixed it. Just a complete coincidence that I had replaced the cluster.

In your case, ensure the sensor is plugged in properly. Then follow the wire until it goes into the car to ensure it is in good condition. Start with that and see what you come up with. If you can get another known working one, swap it in.
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ron
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Re: Speedo signal lost

Post by ron » Sun Feb 11, 2018 2:31 pm

monoi wrote:
Sat Jan 13, 2018 6:01 pm
So nowhere near when I fiddled.

In the spirit of it must be something I did, the other thing I did was to remove the cam cover to change its gasket. So I removed the air box, MAF and the rubber hoses. I also disconnected the plugs to the MAF and idle sensor (I think that's what it is called). I was left with another connector, splitting off the MAF wiring loom, when refitting but I didn't think it was connected to anything and now I'm not so sure.

http://s33.photobucket.com/user/monoi2/ ... w.jpg.html

Does that 3rd connector go somewhere? Would that have an effect on the speedo?
You have PM.
They are ALWAYS rustier than you thought!!!!!!
'88 High line.
'85 M #228
'85 M #207
'80 735i

monoi
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Re: Speedo signal lost

Post by monoi » Sun Feb 18, 2018 5:49 pm

Finally got round to lift the car and have a look at the speed sensor in the rear differential, and as luck would have it, one of the wires was broken at the plug. Repaired that and all is well.

Funny how it decided to happen whilst the car was not being used.

Anyway, on to the next issue...
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raykoke
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Re: Speedo signal lost

Post by raykoke » Sun Feb 18, 2018 9:09 pm

monoi wrote:
Sun Feb 18, 2018 5:49 pm
Finally got round to lift the car and have a look at the speed sensor in the rear differential, and as luck would have it, one of the wires was broken at the plug. Repaired that and all is well.

Funny how it decided to happen whilst the car was not being used.

Anyway, on to the next issue...
Make sure the wire on the front diff is ok. They likely will fail at about the same time.

:D

No, that's ok; I'll find my own way out.

:D

Cheers,

Ray

(Now you know why no one invites me to parties anymore :D )
p.s. Good work! :)
'85 ///M635

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