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Discussion Starter · #1 ·
Hey everyone,

I need your help fixing what should be a simple wiring problem.

The dashboard dimmer (on my 1994 saab 900s 16v non-turbo) has an intermittent connection.

The symptoms are: the entire console (dashboard, radio, heating, everything) loses its pleasant green backlighting. As a result, at night I cannot see my speed !!

I traced the problem to the plug which feeds into dashboard dimmer. THere are about 15 wires on this plug. Depending on which way I pull them, the console will get its lighting back momentarily, until it intermittently turns off again...

( I am willing to solder the wire(s) in question to its corresponding terminal on the dimmer control, in order to skip over the intermittent plug-to-terminal connection.. )

My question is : which wire(s) (in the plug that feeds the dashboard dimmer) is/are most likely the one(s) causing the problem ??


help !!
 

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Hi, I've got the same problem.
It's not likely to be an intermittent connection, more likely the culprit is the trimmer inside the dimmer assembly.
I'm going to change it with a new one this weekend, seems really not a hard thing to do.
I'll let you know if the operation will be successfull and maybe make few photos.
 

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Discussion Starter · #4 ·
Can I open up the dimmer switch, and "short it out" so the light stays on max brightness all the time ?! ANyone try this ???? (I don't feel like junkyard scrounging for a dimmer switch...)
 

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Discussion Starter · #6 ·
Why go through the trouble? Because I want to have it working ASAP tonight or wednesday (if possible)... way before the 1+ week it would take to receive the ebay item.

All I need is the pinouts of the plug, or advice on how to jumper it to max brightness...Any suggestions ?
 

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ccoleman said:
All I need is the pinouts of the plug, or advice on how to jumper it to max brightness...Any suggestions ?
The pinout has been posted here:

http://www.saabcentral.com/forums/showthread.php?t=114289

I may not be as simple as it seems. According to the Saab WIS, the "rheostat" supplies a PWM (pulse-width modulated) signal to control the lamps, not simply a variable DC voltage.
 

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Discussion Starter · #8 ·
PMI said:
It may not be as simple as it seems. According to the Saab WIS, the "rheostat" supplies a PWM (pulse-width modulated) signal to control the lamps, not simply a variable DC voltage.
By pulse-width modulating the 12V power to the lamps, that is how the dimming effect is achieved (it is a cheaper more effective way of getting variable lamp brightness than by feeding a variable voltage to the lamps).

So if I don't care about dimming, I just feed 12V straight to the lamps (only when the headlights are on though!).

( From the pinout, I bet that "unknown" pin is a signal or a switch that indicates when the headlights are on... so you can run without dash lights during the daytime... )
 

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Discussion Starter · #9 ·
The Solution !!!!!!!!!!

I found the solution to fix my console's dimmer!!!!!!!!!!!

First of all..... THANKS to the other posters for what you contributed, which gave me enough information to experiment with until I found the solution.

And so I'm posting my solution here to help the next SAABer with no dimmage to fix that dimmer and get into the land of sweet dimmage (to paraphrase SaabHerb).



CCOLEMAN'S FIX FOR AN INTERMITTENT SAAB DIMMER


Quick summary:
The cause of my dimmer operating intermittently such that we lost all console lighting, turns out to be... drumroll please... OXIDATION ON THE DIMMER's PLUG and IN THE SOCKET that it plugs into !!!!!!!!!!


I found the cause of the intermittent loss of all console lighting as follows:

I took apart the dimmer and saw that the control arm and rheostat were moving correctly when you would scroll the dimmer knob up and down. It is thus most likely that the rheostat is GOOD. Also there were no burned traces or parts on the circuit board, so most likely that the entire circuit was GOOD also. It was most likely something else causing this intermittent losing of all lights on the console.

My guess of the cause of the problem:

My next best guess was a loose connection between the dimmer unit and the socket it plugs into.

2. I noticed some blackened areas on the dimmer's plug. So I took a kitchen steak knife and scraped off the grayish and black layer of oxidation from the plug surfaces (both sides).

3. I plugged the dimmer back into the socket. It was still working intermittently.

Finding the solution:
4. I tried to back the dimmer's plug out of the socket by about 0.5 cm. Eureka. Now the dimmer works RELIABLY ALL THE TIME !!!!!!

5. This tells me that oxidation remains on the deepest part of the inner surfaces of the socket's metal contacts. But cleaning those is going to be tough since you need to get inside there to be able to clean or scrape the socket's contacts. Any suggestions on cleaning the socket's inner contacts ?????
 

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Congrats on your reults.


I would try some contact cleaner. Spray it in the plug, plug the connector in and unplug, spray again and do this a few times. Should work unless one of the connectors has pulled back from the plug. Look closely for that.
 

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Discussion Starter · #11 ·
To SaabHerb and all others !!

I sprayed some Contact Cleaner onto both sides of the metal tabs on the back of the dimmer, plugged the dimmer into the socket, and bang! The socket's contacts AND dimmer's contacts are clean enough so that, now the dimmer works perfectly.

Full functionality achieved... for a total cost of... a few sprays out of a $4 can of canadian tire electronic contact cleaner, which I already had !!!
 

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Hi

nice quick fix!:D

i had the same issues but it was my dimmer unit not the plug which lay at fault.

basically i resolder`d the main board and made a cracking job,even replaced the 3 pin dimmer dial which the little plastic arm goes in, which then attaches to the dimmer roller(the bit you roll up and down to adjust):D

no damn joy though!!

got a scrap unit and its perfic again.

it was a tad wierd when driving at night and all of a sudden you`d loose the whole dash light(speedo etc):eek:
 
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