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Discussion Starter · #1 ·
Help please.

This mornig while sliding my way to the saab garaf=ge to book the car in for it's service (no.13), and to pick up my new dipped headlight retaining spring clips, the speedo dies.

Nothing, speedo and milometer dead, SCC stopped too, no average, speed alert, distance to go stuck etc.

also no cruise.

Does anyone know the pin out of the sensor, colours, common probs etc? is it likely to be the little dynamo bit, the cabling or the gear in the box?

How does one dwebug, what voltage does the dynamo/pulse generator give?

Andrew.
 

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If you're lucky, I'll be the widget drive thingy at the end of the cable that's on the 'outside' of the box.....
If you're unlucky (as I was) it's the plastic ring thingy that fits on the differential....

Has the engine started misbehaving yet..? With no speed signal the ECU gets it's nickers in a twist, this started happening on my Aero about 2-3 days after the speedo stopped working.

That's how I ended up with having a LSD fitted....
 

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Discussion Starter · #3 ·
Engines not misbehaving yet, and TCS is still working (thankfully) but I've only done 20 miles.

I'm going to take the dynamo bit off and thry spinning it by hand/drill to see if i get a reading.

I'm hoping it's not the internal bit, but the gearbox does make a bit of noise on the overrun in low gears until warmed up nowadays.

So how are the internals fitted. you say a rin with the differential, and what, a nylon cog of something to take the output up to the dynamo?

Maybe it's just the fitting under the dynamo bit, but the haynes is useless there!!! doesn't say anything about removal.

I know that I need a clutch soon, 130,000 miles and 250bhp have taken their toll on the original, and takeup often gives a strange noise now and the clutch pedal is so heavy compared to the Carlsson's one.

Maybe that stage2/3 speedparts wont be a january present anymore.

Andrew
 

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I do not wish to be the bearer of bad news but...
the plastic gear thingy on the speedo drive failed on mine..cost of part 50 p
cost to fit it £1200...ohyes admitedly at a dealer ..
if it has to come out my best advice is to get an gearbox rebuild @ abbotts... a relative bargain at about £600 ..new bushes .synchro etc..a really good job
Ps you have about 50-100 miles till the ecu calls it a day and it goes into limp home mode

sorry
 

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I've also had this happen due to corrosion in the connector at the sensor. However, this showed up as an intermittent fault at first, which you haven't mentioned seeing.

The sensor can be removed for inspection. The little plastic gear aeropilot mentions is a common problem and it should be apparent on inspection if it is damaged. The big plastic ring gear on the differential is also not uncommon, and is a gearbox-out job, unfortunately. That's how my CSE got a Saab recon. gearbox only about 1000 miles before I bought it, and how aeropilot got his LSD, as he says.

There is a technical bulletin about this gear, which says:

Speedometer - Inoperative

SI N0. 471-1936

PI No.

Date April 1998

Distr. all

9000

Speedometer stops working

Cars affected

Saab 9000 M96-98, manual gearbox up to and including serial number P56262

Background

Due to varying quality of materials used in the speedometer gear wheel (A) or to initial damage during assembly of the gear wheel in production, the speedometer in the above cars may stop working.

When changing the gear wheel, place the new gear in boiling water for 45-60 minutes before fining. This will prevent damage that can otherwise occur when the gear is pressed onto the differential housing.[/b]
The sensor has two white wires running to it. No idea what shape the speed signal is (sinusoidal, probably), but the frequency is 9832 cycles per kilometre. Since the wires are the same colour, I assumee the signal is unpolarised.

This signal goes to the speedometer, which supplies everything else (including Trionic) with a signal (squarewave, I think) of 2458 pulses per kilometre. This works on a 15V supply, so I assume the amplitude of the pulses is 15V.

While a faulty speedo can't be ruled out, it appears to be rare compared to speed sensor problems. i.e. wiring to the sensor, drive to the sensor or a fault in the sensor itself.

[Edit - forgot to say the sensor is held by a single screw and clip]
 

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Originally posted by ylee coyote:
[qb]if it has to come out my best advice is to get an gearbox rebuild @ abbotts... a relative bargain at about £600 ..new bushes .synchro etc..a really good job[/qb][/b]
And for £920 + VAT, they'll do all that and fit a limited-slip-diff too.
 

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Originally posted by Scaero owner:
[qb]So how are the internals fitted. you say a rin with the differential, and what, a nylon cog of something to take the output up to the dynamo?[/qb][/b]
Yes, there is a plastic gear at the bottom of the sensor that meshes with the gear on the diff. If it is a mechanical problem, it might be this gear, which I think is available separately, and not hard to fit, I'm told.
 

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Originally posted by BillJ:
[qb]Yes, there is a plastic gear at the bottom of the sensor that meshes with the gear on the diff. If it is a mechanical problem, it might be this gear, which I think is available separately, and not hard to fit, I'm told. [/qb][/b]
Just ordered this from my dealer. He quoted me £11.
 

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Discussion Starter · #10 ·
I forgot to say that mine is the old style 91-93 gearbox, not the newer 94 on one.

If this bit is suseptable to failure, I'm surpriesed that the carlssons one is still ok, it did 25,000 miles under my ownership (and several under the prev owner) with all the filing from 3 destroyed reverse gear cogs in there.

I think the part is 87 27 232, but I'm not to sure what I'm looking at on the EPC.

But as BillJ said, £600 for a abbott rebuild, £920+vat to inc LSD is a lot less than the £1200+vat saab charge for an exchage box (exc fitting).

I'm just glad that last year a chappie was paying that for his Aero when the slieves siezed in 1st when the bearings went, and I was able to borrow his reverse gear set for mine (for £80 and all the help I needed from the saab garage).

also,
place the new gear in boiling water for 45-60 minutes  [/b]
that will mean it definitly cooked (or sterilised!)

Andrew
Still hoping it the easy thing.
 

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Discussion Starter · #11 ·
Also, thinking about it, for the last 3 or 4 years, the needle has bounced from 0-20 when creeping forward or backwards very slowly, but has always been rock steady when traveling above 1-2 mph.

Also also, being lazy, does anyone know how many teeth there are on the abs sensor trigger, it might be time to consider upgrading the car to a ABS driven speedo. my wheels give a rolling circ of 1960 mm, or 510.2 revolutions per 1 KM.

Now, if the ABS wheel has 19.27 pulses per turn, that would give me my 9832 pulses per KM.....
 

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There are 46 teeth on each wheel, each generating a single AC cycle (waveform amplitude is between 0.15 and 0.7 volts). i.e. 46 * 510.2 = 23469.2 cycles per km. You'd have to shift the frequency, but at least it is easier to divide down than multiply up. You need to divide the sensor signal by 2.387.

Did you really expect each driveshaft/hub to have 19.27 teeth on it?

Are you aware that the 9-5 uses one of the rear ABS sensors to measure speed? (Thanks for the info, Leon). I imagine one benefit is that you get an accurate reading even if the front wheels break traction.

Anyway, given the cost of replacing the internal drive ring, you might have hit upon a viable solution!
 

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Discussion Starter · #13 ·
BILLJ, Aeropilot, Ylee,

Did you deliver you car's to Abbotts, or just the box?

£920+vat seems a good price for rebuild and LSD when the site list LSD as £720+vat by itself

hmmm

Also, new bearing and syncros' would be goos (bearing are prone to pitting, synchros are still ok). Clutch needs changing anyway.

Abbotts may be on the cards, but john and julian will then have to wait for a stage 3 sale.
 

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How the 9-5 does it...
Speedometer

The main instrument unit is fitted with an electronic speedometer. The TC/ABS control module receives speed information from the LH rear wheel speed sensor. The information is processed and sent continuously to the main instrument unit control module connection 10 (K12).

The information in the form of a square wave pulse varies periodically between B+ and 0 V. This takes place 29 times per wheel revolution.

With the wheels stationary, the voltage may be either B+ or 0 V.

The main instrument unit uses the frequency to calculate the vehicle speed.

The speedometer is supplied with current and is controlled by the main instrument unit control module, which also sends information on the speed to the bus.
 

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And I drove my car to them, making sure not to use large amounts of boost to cause the clutch to slip. The £920 + VAT includes removal/replacement of the gearbox. That alone makes it good value, never mind the rebuild and any new parts. From Mark E's experience, though, I gather that if there are any parts other than synchros and bearings that need replacing, they'll cost extra. Sounds fair.
 

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Originally posted by ylee coyote:
[qb]giles met me @ 11pm at scotch corner !![/qb][/b]
Wow! That is good service. Giles has offered to bring my car most of the way here, although if it's near the end of the week, I'll be tempted to wait until Saturday and pick it up from Abbott. Then I get to give it a good check over and a nice long drive home.
 

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Discussion Starter · #19 ·
So, I got up early this morning and got the car on axle stands.

Found my spanners, managed to disconnect the cable junction one handed and started to undo the little dynamo bit.

2 hrs later, it's still in there! The speedo transducer is turning but not coming out.

After this setback, (i wanted to make sure it was the box not the sender) I got out my Digital voltmeter.

Transducer has 338 ohms resistance.
Started the car and put in reverse. output was:-

0V (ac or dc)
no pulse width
no dwell
0 frequency
no period time

So it looks like the gearbox transducer combo is dead, and as I cant get the transducer out to prove it that (but it looks ok as it has 338 ohms), and it's unlikely that the metal drive cable down is broken, it must be the gears in the box. Bu99er!

Car goes in for a service Tuesday. shortly after a call to Abbotts is on the cards.

Andrew
Batter, scraped and depressed.
 
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