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Discussion Starter #1 (Edited)
panel dimmer dead - is bypass possible?

Ok. So this sounds like the ultimate Ghetto repair, but humor me a bit . . .

Does anyone on this forum know the pinouts for the instrument panel dimmer switch. I'd like to just bypass the @#$%^&*'ing thing at its brightest setting. This is where I always have it set anyway.

I'm shopping to replace the thing, but would simply like to buy a little time while I chase down a reasonably priced switch ( the dealer must believe his are made of solid gold).

Driving at night is really a pain with no panel lights.

Thanks in advance . . .
 

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Discussion Starter #3
Can't argue against that. I'll check it out. Thanks.

Anyway, I played Sherlock Holmes and worked out the pinouts the hard way. So I might as well post them here for anyone else who may need this information. Maybe some day the supply of cheap used controls will dry up before us Saab geeks get tired of driving these cars. :cool:

On the back of the dimmer switch the posts are numbered, so here's what I found:

1 - chassis ground
2 - radio & seat heater controls
3 - main instrument cluster & SID
5 - fog light controls
7 - 12v (+)
9 - couldn't determine this one

The reason I couldn't determine post 9 could be that my bulbs are dead. I never did get my heater controls to illuminate.

The best part is, I only popped one fuse in the process. :p
 

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BustersTurbo said:
Can't argue against that. I'll check it out. Thanks.

Anyway, I played Sherlock Holmes and worked out the pinouts the hard way. So I might as well post them here for anyone else who may need this information. Maybe some day the supply of cheap used controls will dry up before us Saab geeks get tired of driving these cars. :cool:

On the back of the dimmer switch the posts are numbered, so here's what I found:

1 - chassis ground
2 - radio & seat heater controls
3 - main instrument cluster & SID
5 - fog light controls
7 - 12v (+)
9 - couldn't determine this one

The reason I couldn't determine post 9 could be that my bulbs are dead. I never did get my heater controls to illuminate.

The best part is, I only popped one fuse in the process. :p
Ok but... how to actually bypass the dimmer?
I live in Italy and can't find any of those dimmers in Europe... just don't want to spend over 20$ for shipping and have to wait centuries for it to arrive from USA...

Thanks.
 

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I wonder if the socket could be wired to dim only parts of the instrument panel. Someone asked about that once. Personally, all I ever want to dim is the main instrument cluster, the buttons backlit in green do not bother me.
 

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Discussion Starter #7
My first step was to determine which wire, using a simple 12v test light, was the 12v (+) source.

My next experiment involved rigging up a short test wire with the appropriately sized spade connectors on either end. My plan was to use this wire as a jumper from the 12v (+) socet to each of the other socets in the plug that connects to the back of the dimmer switch.

By alternately plugging the opposite end of my jumper wire into the various socets in the plug I found that I could get the corresponding instrument panel lights to illuminate. That's how I came up with the pin assignments listed above.

The only problem was not knowing which one of the plug's socets was the chassis ground. As soon as I connected the opposite end of my jumper to this socet, the fuse popped, obviously.
 

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BustersTurbo said:
My first step was to determine which wire, using a simple 12v test light, was the 12v (+) source.

My next experiment involved rigging up a short test wire with the appropriately sized spade connectors on either end. My plan was to use this wire as a jumper from the 12v (+) socet to each of the other socets in the plug that connects to the back of the dimmer switch.

By alternately plugging the opposite end of my jumper wire into the various socets in the plug I found that I could get the corresponding instrument panel lights to illuminate. That's how I came up with the pin assignments listed above.

The only problem was not knowing which one of the plug's socets was the chassis ground. As soon as I connected the opposite end of my jumper to this socet, the fuse popped, obviously.
Ok now I understand :)
Thanks a lot.
 

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Is there any way that electrical contact cleaner could be used to renew the rheostat ?

Or is that totally shot ?
Could 7 and 5 (internal) be bridged to bypass the rheostat ? Admittedly far-fetched as one would have to open up the dimmer - probably impossible ??

And, at least beyond the front switch knob, would not the Opel dimmer be identical ??
 

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earthworm said:
Is there any way that electrical contact cleaner could be used to renew the rheostat ?

Or is that totally shot ?
Could 7 and 5 (internal) be bridged to bypass the rheostat ? Admittedly far-fetched as one would have to open up the dimmer - probably impossible ??

And, at least beyond the front switch knob, would not the Opel dimmer be identical ??
The rheostat used in the dimmer (at least in my 1995 dimmer) is a closed one.
I've tried to spray some electric contacts cleaner on it, but it seems it couldn't reach the contacts inside.
I'm also afraid that the contacts could be actually corroded.

It's not so hard to change just the internal rheostat, if you know how to use a welder.
My problem is I can't even find a rheostat like that in the electronic stores here...
 

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hkayssi said:
I think that one is incompatible with BustersTurbo's NG 900 or 9-3. Because my 1994 NG 900S requires the rheostat with the 9 pins on the back. This one on ebay looks like it has 2 or 3 pins on the back, and it came from a 1991 9000.

Be careful... ya want to avoid getting the wrong one !!
 

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BustersTurbo said:
.... By alternately plugging the opposite end of my jumper wire into the various socets in the plug I found that I could get the corresponding instrument panel lights to illuminate. ....
So BT... are we to conclude that your Ghetto Fix for the Rheostat is to patch the 12V (pin 7) to each of the various instrument cluster area lights (pins 2,3,5) ??
 

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Among the litany of things to fix on my recently acquired 95 900SE v6 was the dimmer switch. I have dash and instrument lights but no dimmer action. The wire from pin 9 was jumpered to the inside of the switch assembly and the pin 9 socket was melted on the plug. So, as I made my forray through the boneyard I came across 900 with a switch. After jumpering in the new plug and installing the new switch I have the same condition - lights but no dimming.
I took the original switch apart (both end come off with a little prying at the plastic tabs) and found that the rheostat was missing.
Also I could see where the pin 9 wire was jumpered to. Anyhow, tomorrow I'm going to take the other switch apart to see if the rheostat is missing that one.
I'm wondering, is there suppose to be some back lighting on the instrument panel? I recall reading that someone mentioned some green lighting.
I have a picture of the dimmer switch board with the jumper but I could not upload it because it was too large. I'll work on that but if you are desperate I could email it instead until I figure out how to decrease the size of the picture file.
 

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SaabHerb, congratulations ..

You have laid to rest the myth that the dimmer switch(at least the older ones) was "non-serviceable".
This is good..
Would it not be quite the thing if a master DIY could repair the dimmer switch using a part from Radio Shack...
One of the eBay problems is that too many sellers have no idea of what a Saab 900 is, worse, they do not care.
To them, the only thing that matters is sell, sell, sell....
 

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Good news! I pulled the dimmer that I got from the boneyard and everything was intact. When I popped the control end a piece fell out. That piece was a little control arm that sits in a slot on the rheostat. I put the arm in the slot, checked te resistance from pin 1 to pin 7 and it varied from 22.6-23.2K ohms so I figured the rheostat was good.
Bottom line - when I put it all back together I still have lights and now I have DIMMAGE !!!
Couple of notes:

1. The rheostat does appear to have an area where some contact cleaner can be used if needed.
2. When installing the control arm in the rheostat put the control piece toward the rear - away from the knob.
3. You have to hold the control knob in place when you snap it back into place so that it will align with the control arm.
4. Small needle nose pliers are a great help and my magnifier light helped also.

** Pin 9 (the wire I said was soldered to the circuit board in my previous thread) is lighting for the Clmate Control. Shorting pins to 12V seems a bit much considering you would have to short pins 2,3,5 & 9.

From what I see there is no need to jumper any wires to get lights if the rheostat works and assuming there are no other component failures in the circuit. Open the switch and adjust the rheostat (the little white piece in the middle) to the extreme to keep the lights on. If the control arm is broken or missing you may be able to do this with a jeweler's screwdriver while the lights are on.

I hope this helps.

Dimmage is as dimmage does.
 

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SaabHerb said:
1. The rheostat does appear to have an area where some contact cleaner can be used if needed.
[...]
From what I see there is no need to jumper any wires to get lights if the rheostat works and assuming there are no other component failures in the circuit. Open the switch and adjust the rheostat (the little white piece in the middle) to the extreme to keep the lights on. If the control arm is broken or missing you may be able to do this with a jeweler's screwdriver while the lights are on.

Well done, but my problem (and few other NG900 I've seen) is actually the rheostat being broken.
In this case, there are only 2 things to try: either change the rheostat o jumper the wires to bypass it.
The first one is what I'll try to do next week end.
I'll let you know if it works and post some pics.
 

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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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You might try Radio Shack to see if they have any spray-on contact cleaner. It used to be called tuner cleaner back when television tuners had huge drum switches built into them. Spray it into the connector, plug it in and out and wiggle it around a few times to help it break up the corrosion.
 

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To jstrowe, and all others on this thread !!

I took your advice, got a can of Contact Cleaner, sprayed some 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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ccoleman said:
To jstrowe, and all others on this thread !!

I took your advice, got a can of Contact Cleaner, sprayed some 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 !!!
Super, How's that wazee pulley woking so far? it's been a year almost, right?
 
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