Scantar's been fighting this for a bit so I'm sure he'll chime in --

Mine has started to do the same thing. Probably the connection to the EDU module mounted on the gauge cluster, or some crusty solder joints lying within the module itself.

The real danger with this is that the module also sends a temp signal to the ECU. With no temp signal input the default is the ECU thinks the engine is cool and won't turn on the fans -- this could cause you to over heat the engine before you know it in city driving with the a/c on...

 

I talk with him outside SC, ohh I know. He thinks it's the ribbon and I think it's the brain. Ive been swapping EDUs and was good for awhile but problem came back. I've had 3 different 9Ks do this same thing. EDU swap fixed it on one '98, I've went through 2 different EDU on another '98 and once Ive caught it on my '94 which I have taken no action on.
On '95 and above it will turn off the stuff you say plus turn off the AC! '94 temp gauge don't talk to the ECU so might effect differently.

 

I swapped my temp/fule gauge and that seams to fixed it for me.
No longtime test yet. I suspect the soldering and nuts behind the gauges.

 

I tried swapping cluster only, had no effect. What year is your car, not listed in your avatar.

 

Here's the bullcarp part of all of this. If we can't come up with a way to either repair or just bypass the edm - or at least the part that sends temp signal to the ecu - the 9K is destined for extinction. This is an issue that is happening with more frequency if you look through the threads over say the last 12 months. That means the edm is aging out...not a good thing!


The edm is essential to the operation of the cooling system. When the right side cluster drops out, the edm tells the ecu that the car is cold and the ecu shuts down the fan. Not terrible if it's winter and you're highway driving. Head Gasket popping if it's summer and you're city driving.


My observation is it does seem to be heat related, as in behind the dash heat related. That tells me that either a solder joint is bad (there are literally hundreds) or it's internal to one of the eeproms or transistors (there are dozens)


Ideally, it would be cool (no pun intended) to be able to bypass the system altogether and send engine temp signal to the ecu a different way, regardless if the gauge drops out...but that takes thinking time, like a weekend camping in the woods thinking time.

 

I've got a pdf of the ECU pin-out somewhere...
The T-5 suite project shows how to add T 5.5 to a C900 so the pinouts exist and a bypass could easily be achieved...

I have to imagine it'd be more accurate at this point too -- having the eng temp reading come into the dash and going back out is using a lot of wiring and bulk head & dash connectors -- any of which can be affecting the resistance / ohms which is translated to eng temp for the ecu to determine best fuel mixture...

 

94 and below dont talk to ECU. Seems to effect OBD2 cars only.

 

Related symptoms?
Just completed another CO to Ohio drive (1300 miles) and intermittently had the following glitch:

The temp and fuel gauge would start reading high -- this would be accompanied by a drop in the voltage gauge readout as well as an actual dimming of the edu (digital numbers of the voltage readout). Very hard to tell during the day but at night it was easy to correlate that the lower the voltage read (went as low as 10.2v) the higher the temp & fuel gauges read.
The headlights did NOT dim when this occurred -- I don't believe there is any issue with the actual charging system but can't confirm...

The car didn't drive any differently this trip although I did notice a slight loss of mpg overall average this trip.

Regrettably I'll have to drive it back to CO in a couple weeks with this problem probably unsolved...
Without a really good wiring diagram I don't know how to even begin with this one...

Once back in CO I'll probably replace the dash cluster since I have a "low mileage" one in stock and hope that solves the gauge reading and occasional drop-out symptoms...

 

In regards to high readouts. My 1994 reads like its about 2/3 temp up. I will not bore you with the story of how I tried to diagnose. The national guard needed to be phoned to find me though. In the end I just trust the IR meter is right and not the gauge. Wonky temp gauge.
I hoard clusters now.
I once went and looked at a near death CL 1998 where dude had a rubber hammer he used to beat the dash board in "just the right spot" to get the T an G gauge to work again. Believe ive told the story. Wanted 1,500 dollars for it. HAHAHHAA. I remember what an idiot he was well. He called me a few minutes after when I left and said "then what's your best offer?" ..
"I was afraid you'd take $400 so I didn't say anything"
Click.

 

Chengny -- regarding your post #21:

1) The printouts you show are for the EDU (dash gauge/display) same item as in your post #15 -- item #210 on the diagram?

2) Aren't there two separate temperature sensors on the engine?
The NTC type sensor between cylinders 2 and 3 is the sensor that sends a signal to the ECU (fuel/ignition control) to influence the fuel mixture.

3) there is another temp sensor on the left hand side of the cyl head. I thought it was this sensor that sends a signal to the EDU (dash gauge/display) And it's my understanding (from your diagrams in post #15) that it is this EDU that controls the cooling fan functions.

It will require extra typing but I think it will be worth it use greater precision in our written communication if it's to be of value in sorting out the temp/fuel gauge problem.
Especially since we're not all working off the same wiring diagrams (I think mines an old Mitchel electrical diagram -- that's why I never post "component #'s from that diagram -- I know it won't match anyone else's...)

Please correct me on anything I've said in this post
Cheers!

 

Seems like you have everything right.

Chengny -- regarding your post #21:

1) The printouts you show are for the EDU (dash gauge/display) same item as in your post #15 -- item #210 on the diagram? Yes, the pinout matrices refer to the pins at the EDU connection.

2) Aren't there two separate temperature sensors on the engine?
The NTC type sensor between cylinders 2 and 3 is the sensor that sends a signal to the ECU (fuel/ignition control) to influence the fuel mixture. Yes, and the other sensor - which is only connected to the EDU - is used for fan/temp gauge control.

3) there is another temp sensor on the left hand side of the cyl head. I thought it was this sensor that sends a signal to the EDU (dash gauge/display) And it's my understanding (from your diagrams in post #15) that it is this EDU that controls the cooling fan functions. Yes. As noted above, that is correct.

It will require extra typing but I think it will be worth it use greater precision in our written communication if it's to be of value in sorting out the temp/fuel gauge problem.
Especially since we're not all working off the same wiring diagrams (I think mines an old Mitchel electrical diagram -- that's why I never post "component #'s from that diagram -- I know it won't match anyone else's...)

The list of components associated with the EDU & SCC - which are collectively referred to as the Trip Computer:




Please correct me on anything I've said in this post
Cheers!

 

Ok, let's do a reboot here because I think we're all getting lost in the weeds. My observation of what happens is this:


* The right side cluster drops out...temp and fuel peg to the bottom.


* The edu flashes a check radiator light and the low fuel light is on


* The cooling fan stops and the air conditioning shuts off


* The cluster can come back to life on its own after a moment or slapping the dash top can get it to come back on. All functions return to normal



Another observation is that this only applies to the cluster dropping out. I say this because I have an intermittent temp reading...sometimes it's on, sometimes it doesn't read...that has no effect on the above observations so it's not simply that the gauge doesn't display. Also, the edu clearly functions in some way because it displays the warnings so it's not just a power loss to the unit itself. It is specific to the reading inputs from the entire right cluster. And, when that output from the cluster is lost, something is doing a job based on that loss of reading, whether it is the edu itself or the ecu

 

So from my (limited) experience -- when the right side cluster drops out:
"* The edu flashes a check radiator light and the low fuel light is on"
I see the low fuel/check radiator light come on at the same time I see my temp/fuel needles bounce back up to a functional reading -- or while driving I don't notice the temp/fuel needles drop to "off" but notice the low fuel/check radiator light come on and assume the needles must have dropped for a moment. Since the low fuel/check radiator lights are part of the start-up sequence when you apply electrical power to start the car I've assumed the temp/fuel gauge "peg to the bottom" has been caused by a loss of power to, or within the EDU.

I haven't had the r/h cluster drop out long enough to know if my fans were also taken out -- 90% or more of my driving is hwy. I only ever hear the fan after driving in the summer when it runs a bit after engine shutdown...

"Also, the edu clearly functions in some way because it displays the warnings so it's not just a power loss to the unit itself."
By this are you saying that your temp/fuel needles are pegged at the bottom BUT you have the check radiator and low fuel light stay on?
That would be a slightly different set of symptoms than mine.

 

They fail to mention that after the ignition switch, the +15 is fed through fuse #13 - and then to the EDU and the warning lights section of the instrument panel. These warning lights:



Which are connected at this pin set:



Just as useless info, the pictogram lights are supplied at this set:



On the other side of the panel - above the pictogram - there is an additional printed circuit. It has 7 pin connections like the one on the other side. There is not much going on over there. Usually just the tach, LH directional indicator and the backlighting. There are provisions for a "lights on" indicating lamp (not used in the US or Canada) and a TCS lamp.






Might as well cover everything. Last are the 2 connections in back of the speedometer. There is a 2 pin and a 3 pin connector:



The 2 pin is in from the signal generator (mounted on the transmission) and the 3 pin is out from the vehicle speed sensor (which receives input from the speedometer itself). That speed sensor signal is used by a number of components:



COMPONENT ID

111 Electronic speedometer in the main instrument display panel.

112 Sensor, electronic speedometer, on the gearbox.

132 Vehicle speed sensor, in the speedometer.

210 EDU trip computer in the main instrument display panel.

241 SCC trip computer in the center of the dashboard.

256 Speed warning buzzer, in the center console's bottom storage compartment.

356 Speed warning control module, at the rear of the bottom storage compartment in the center console.

430 Saab Trionic control module, in the engine bay at left on the bulkhead partition.

508 Cruise Control system control module, adjacent to the battery tray.

510 Motronic 2.8.1 control module, in engine bay behind the bulkhead partition.

589 Saab Trionic OBDII control module, in the engine bay at left on the bulkhead partition.hhhh

 

Ok, re-reading the thread for the umpteenth time, one image that chengny posted early on shows the back of the cluster, ribbon tape and id's the pin functions.



One thing thing that has me shifting my thought process...pin 2 gets constant 12v to the gauges from the edu(m). If that's lost, obviously the gauges will drop out and obviously the edu(m) will then go through its courses of action...lighting the low fuel lamp, flashing the check radiator warning and then cooling fan shuts down, a/c shuts down until that 12v signal gets back to pin 2


Slapping the dash top over the area of that gauge cluster seems to be a common response from people so there's a start...

 

Ok, re-reading the thread for the umpteenth time, one image that chengny posted early on shows the back of the cluster, ribbon tape and id's the pin functions.



One thing thing that has me shifting my thought process...pin 2 gets constant 12v to the gauges from the edu(m). If that's lost, obviously the gauges will drop out and obviously the edu(m) will then go through its courses of action...lighting the low fuel lamp, flashing the check radiator warning and then cooling fan shuts down, a/c shuts down until that 12v signal gets back to pin 2


Slapping the dash top over the area of that gauge cluster seems to be a common response from people so there's a start...

That was my symptoms on the car and I couldn´t change the EDU the spare wasen't for a automatic.

 

https://www.turboimagehost.com/p/39933589/Copy_of_saab-9000-instrument-cluster.jpg.html

Wow! I don't think I've ever seen all these lights...
And did you reset your odometer to 0000001 ?!

I should probably expend a can of contact cleaner and replace all the bulbs before installing my spare cluster/edu assembly...

 

https://www.turboimagehost.com/p/39933589/Copy_of_saab-9000-instrument-cluster.jpg.html

Wow! I don't think I've ever seen all these lights...
And did you reset your odometer to 0000001 ?!

I should probably expend a can of contact cleaner and replace all the bulbs before installing my spare cluster/edu assembly...

I think that's a rendition of the cluster. I've never seen the oil level or gear box display

 

Schematic and brief explanation of the "Combined Instrument" (i.e. the fuel tank & coolant temperature gauges):



The combined instrument (fuel gauge/engine temperature gauge) are both two pole instruments where one coil in each instrument is fed with about 12 V from control module pin 22. Both gauges are grounded to grounding point G8.

Fuel level gauge
The control module feeds 1 - 9 V on pin 24 to the second coil in the fuel gauge and in this way controls the gauge reading.

Engine temperature gauge
The control module feeds 1 - 9 V on pin 30 to the second coil in the engine temperature gauge and in this way controls the gauge reading.


The way I explain gas gauge operation on other (GM truck) forums - edited for a Saab 9000:

The fuel tank sender is connected to pins 33 & 26 of the EDU (via the WHT & BLK wires). A variable ohmic value - which is a function of tank level – is generated by a float that drives the sender’s integral wire wound resistor. The EDU receives the resistance value from the sender and then uses that input to generate a variable voltage (1-9 VDC) on pin 24 – that voltage is applied to the gas gauge at pin 1.

The variable voltage output from pin 24 of the EDU - when connected by the GRN wire to pin 1 of the printed circuit - forms the "sensing leg" of the gas gauge. Pin 1 on the printed circuit is connected to the positive side of the sensing leg’s coil. The negative side of the coil is connected to ground on pin 5.


The higher the voltage that the EDU applies to pin 1 ,the greater the electro-magnetic force created by the coil. Consequently the force that it (the measuring coil) exerts on the gauge's magnet increases. The magnet is attached to the lower end of the indicating needle.

In addition to the sensing leg, there is another - opposing - circuit called the "control leg". It is identical to the sensing leg in every way except that the positive side of its coil always receives a full 12 VDC signal from the EDU on pin 2 (as opposed to the variable voltage the sensing leg receives). The control leg’s coil is located on the opposite side of the magnet from the sensing leg’s coil. It's negative side is also grounded via pin 5.

So what you have is; two coils located on either side of an indicating needle - AKA the "ray". The ray is pivoted somewhere in the middle and has an integral magnet mounted at the bottom.

These coils create their own magnetic fields - the strength of which is a function of the electron flow (i.e. current) passing through them. When these circuits are energized - by turning the ignition switch to the RUN position - the opposing magnetic fields begin to "fight it out". Each coil tries to pull the magnet - mounted on the needle - towards itself.

Due to the fact that it always sees full battery voltage, the current flow through the control coil is essentially constant (as is it's magnetic force).

On the other hand, due to the variable voltage signal generated by the EDU (as a result of changes in the fuel tank level), the current flow/magnetic strength of the sensing coil can range higher or lower.

The location of the two coils - to the magnet - is such that:

1. The control leg is always trying to peg the indicating ray to the FULL end.

2. The sensing leg is always trying to peg the ray to the EMPTY end.

 

I think I'm going to have to take apart one of my spare clusters and look at this common ground.



Going through this...the loss of reading must be either from the constant 12v input or the common ground point failing. I doubt that it's from the variable inputs because the loss of reading is total and it affects the entire cluster. Ground failures in general are much more common throughout the whole electrical buggiverse so that's where I'm leaning.



I think this is getting close...

 

I have to re-think my re-thinking here. Despite the fact that the grounding point would be the likeliest of suspects, the fact does remain that changing the edu does solve the issue. And given that the turn signal indicator is on that same common ground you'd think that someone would have noticed and mentioned that before.


I'm back to this being a power-in to pin 2 issue from the edu

 

Since I've only had the temp/fuel needles peg down for brief amts of time I've never had an opportunity for testing...

When your needles pegged down for a longer period of time, and the low fuel & check radiator lights came on. Did the needles stay down or did they resume function after seeing the low fuel/check rad lights come on (and go out after ~4 sec?)

 

If you suspect that needles are positioned incorrect, you can simply pull needle out (use fork etc).
Then input 12V to pin 2, 4.5V to pin 7 (temp gauge) or pin 1 (fuel gauge) and gnd to pin 5.
Wait for 30 sec and insert needle to center position.

 

In thinking about this, and hypothesizing with the KISS principle coupled with Occam's Razor...it would seem that the simple solution to the issue would be to find a constant switched 12v source and tap it right into pin 2


Tell me why I'm wrong

 

I'm thinking that would keep your temp/fuel gauge accurate BUT might not solve the (greater) issue of the EDM "thinking" the power is off and therefore NOT powering the cooling fans as needed...

I think the gauges losing power is a symptom of the EDM effing up...
The temp gauge does not control the fan --

Also -- if the EDM is not putting a voltage signal out at pin 2 and you put power to pin 2 from a different source -- be sure and isolate 'that' power source from the EDM -- there's no telling how the EDM might react to a 12v input where it's supposed to be delivering a 12v output...
(well, there IS knowing but w/out a full circuit board diagram of the inside of the EDM to look at there's no way for ME to know, so I can only urge caution.)

 

Is EDM EDU (Electronic Display Unit)?
EDU reads sensor(s) and send voltage feed to gauge(s).

 

Correct.
EDM electronic display module
EDU electronic display unit
They are the same thing

 

I'm more convinced than ever now that supplying 12v to the gauge cluster from a different source will be the permanent fix.


Off the paper and into the practical now...

 

Is there someone that have tried it yet ?


(My fix with changed temp/fuel gauges module didn't work the fault is back)

 

Can the ignition switch not cause these symptoms? I've got a 1997 2.3 Auto mis-behaving. I swapped out the ignition barrel and for a couple of weeks all seemed fine. Suddenly the gauges dropping out is real bad. Yes low fuel light comes on and it sometimes flashes. It would be brilliant if we could suss this out.

 

The ignition switch has nothing to do with it, or at least not in my 3 go arounds with 3 different 9000s. I will tell you what I know after a few years of experiencing this and my solution.

Simply clean all the ribbon connectors on the back of the cluster and the connector on the cluster. I learned about this recently, though I still have the dash cover off but haven't seen it happen since. I learned this from someone quite familiar with the problem.
OR
separately hardwire your cluster with separate 12v power. I haven't went down this wormhole but have with C900 and failed overhead dash illumination lights.

 

When my gauges drop out the right turn signal still works correctly in the cluster.

 

Gauge cluster dropping readings

Hello,
As I am new to Saab, I am finding this car different than most cars I have owned and worked on. The car had sat for 4 years until we had it moved up here. I got the car running. I replaced the gas tank, replaced the air filter, replaced the spark plugs and cleaned out 4 years of leaves and grass.

I am trying to get this car n the road and things have been going well. But, I have noticed that the gauges are not operating and the lights on the dash do not even come on now. The car starts and runs with the only thing working is the turbo booster gauge. Even the tach and speedo do not work.

It seems that the dash is one of the issues and the other is the EDU? Is this the ECM on other cars which is located on the drivers side, under the cover, next to the windshield in the engine compartment?

Can a new EDU be had? How about a dash? I know that the alternator is charging well.

Any help would be appreciated. We do have a couple of Saab specialists in the Raleigh area, should I send the car to them?

 

Take dash cap off And clean all the connectors w contact cleaner on the back of the instrument cluster/panel and this problem will go away In my experience. It was a long and sordid one.

 

Your problem is more than what mine was just for the temperature gage and fuel gauge not working check fuses first the EDU is replaceable you need to do as I described to get to it anyhow. ninety ninety four to ninety ninety eight are compatible with each other the only difference being one is for an automatic transmission and the one is for a manual

 

To clarify,

"It seems that the dash is one of the issues and the other is the EDU? Is this the ECM on other cars which is located on the drivers side, under the cover, next to the windshield in the engine compartment?"

The EDU is a unit attached to the bottom of the instrument cluster. It contains the pictogram lights display and gear position/fuel consumption etc.

The ECU lives, as you say, under the "aquarium cover" as we call it, ahead of the bulkhead.

You will have discovered by now that the reason the boost gauge works is that its not electronic!

Keep us posted.

Doug

 

Gauges dropping out today. Main beam indicator light still works as does the pictogram when both temp and fuel gauge don't.
What would happen if an EDU from a manual car was fitted to an auto or vice-versa?

 

automatic and manual have different criterion for the illuminations on the display, like automatic shows PRND321 for example and a manual would not, has the MPG instead or whatever, they're different is bottom line, its why I said you use the one specific to the transmission to your car. far as I know you need to use 1995-1998 EDU, though I don't know what year your car is as it's not in your avitar, 95-98 is where I have experienced the issue, the extent of my experience with it, there's 2 variants, manual and automatic EDU choose from years I described.

You're likely doomed with this issue though. Ive chased it endlessly with 2 9000s I have and it doesn't seem curable. Only if you directly power it with 12v seems to be a solution. I haven't climbed into that wormhole yet.

 

This is a post from uksaabs.
"recently I was observing randomly the fuel level and the engine temp would just drop out, low water level warning would come on, then after maybe 30sec / min - the gauges would pop back up but not always to the correct position ( a bit of a pain ref: the fuel gauge) it would do this at random intervals - - the fix was - the 40amp fuse for the cooling fan had blown - - is this a weird and wonderfull SAAB signal of this failure ?"

I have a 1997 2.3 auto and 3 1997 2.3 manuals and 1 1995 2.0 auto.

 

You don't have one of those in line fuses on your 1997. Cooling fan changed in 1994, was the final year they did that, maaaaybee, 1995. Definitely not 1997. This is not your cure.

You could verify this buy looking online and seeing the different cooling fans between those 2 years. Esaabparts is good site to do that on.

There is also probably nothing wrong with your EDU, btw, probably a bad ground somewhere. Ive been on this struggle for 2 years with various 9Ks

I almost thought I had it fixed this last time. Like I said, I may look at diagram and figure out how to give it separate 12v power. It's losing power, or it's losing ground, more likely the latter. tried cleaning all contact throughly behind cluster. Might sand the rest of grounds on car. I believe there is about 10 plus ground points on a 9K off top of my head.

 

So, I was wondering if you need to ground the metal dash to the metal structure? And where would you attach 12 volt supply to the back of the dash?

 

id use the cigarette lighter power as it's switched and close.