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Registered
1992 500SL
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13 Posts
Discussion Starter #1
I recently purchased a '92 500SL and am having an issue with backlighting on the entire dash. All warning indicators light when ignition key is turned on and all gauges work. When the light switch is turned on there is no illumination on the dash or center console.

The exterior failed lamp light comes on, but all exterior lamps seem okay.

I have checked fuses and checked to see if 12V is coming to the illumination circuit on the instrument cluster.

There was an aftermarket radio installed which I removed and found that the gray/violet wire which also feeds the cluster is just loose.

Like I said no cluster backlighting or console llighting.

Any suggestions would be greatly appreciated.

David
 

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Registered
SL-LESS (for now) and 2002 Jaguar XJ8 Executive
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270 Posts
A bit obvious maybe but have you tried the light dimmer?
You’ll be surprised to hear how many people forget to turn this little knob...
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #5
I've turned the dimmer. I have also checked the resistance on the potentiometer and the resistance changes as I turn the dimmer knob.
 

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Sith Lord
72 280SE 88 560SEC 92 E500 6.0 95 SL320 14 GLK350
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11,813 Posts
Is your license plate lit?

Could be fuse #1. Or #5. That loose wire you mentioned could have short-circuited something.
 

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Sith Lord
72 280SE 88 560SEC 92 E500 6.0 95 SL320 14 GLK350
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11,813 Posts
Oh, and don't forget to update your profile with location and model year before Mick comes in.
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #8
The license plate is lit, I checked fuses 1 and 5 again and both are good. I checked the gray/violet wire behind the radio and when the lights are turned on I am seeing 12V. The power that feeds the illumination circuit appears to be there, but it is not lighting the lamps.
 

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Registered
2000 Obsidian Black Metallic Mercedes SL 320 V6
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4,527 Posts
Oh, and don't forget to update your profile with location and model year before Mick comes in.
Lol elbeik.

Anyway dmcraesho hello and welcome in our big friendly and international family :D. Please update your profile with your car, year and location to help us hep you in the best and quickest possible way. It's very important for us you do this.

Cheers.
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #11
The light switch is on, and I have tried adjusting the dimmer and still no lights. I am assuming the problem lies in the dimmer circuit. I have pulled the cluster and checked the potentiometer that is the dimmer switch and it checks out just fine.

I realize there is more to that circuit than just the potentiometer, but with out a diagram or a knowledge of what components are in the circuit it is kind of hard to locate the culprit.
 

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Sith Lord
72 280SE 88 560SEC 92 E500 6.0 95 SL320 14 GLK350
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11,813 Posts
It sounds like a bad dimmer. I assume even your climate control is off, gear lever et al.
 

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Greek God of the R129
SL500-500SEL-190E
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8,391 Posts
You have multiple problems.

Check the light bulbs to be original replacements.
Especially the WATS.

Behind the fuse box are the relays remove the largest one, there no need to disconnect it.

This is the relay for the burned light bulbs, etc.
Lightly tap the sides, see if something changes.

Be gentle it is female sensitive. ;)

Regards,
aam.
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #14
Yes the climate control, gear shifter, etc... are all not lit. I am assuming there is a problem in the dimmer circuit. I have removed the cluster and will try to track down the faulty component.
 

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Moderator
SL55, 300SE, GL450, Daytona 955i
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10,293 Posts
I ve seen bad stereo shops and amateurs damage the dimmer in the cluster when working on the head unit, and shorting the illumination terminal of dimmer line...

so you ARE on the right track, checking the cluster...
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #16
I have done some troubleshooting but without much luck. It is a little hard to trace the circuit with out a schematic. I have a question related to this and hopefully not off thread. Which newer clusters are interchangeable with this one? Specifically what year and model cars? My best bet may be to find another cluster. Will the newer digital clusters work? Thanks for any input.
 

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Registered
SL-LESS (for now) and 2002 Jaguar XJ8 Executive
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270 Posts
I have done some troubleshooting but without much luck. It is a little hard to trace the circuit with out a schematic. I have a question related to this and hopefully not off thread. Which newer clusters are interchangeable with this one? Specifically what year and model cars? My best bet may be to find another cluster. Will the newer digital clusters work? Thanks for any input.
Hey, it's your thread. You can go in any direction with it.
This has been discussed just last week, here is the thread:
http://www.benzworld.org/forums/r129-sl-class/1558372-question-car.html

Replacing for the same as you already have is always cheaper than going digital. It will bring extra costs along with it.
Try ebay, they are being advertised regularly.
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #18
I would like to replace with one like the original but I am having a hard time locating one. Would one from a '91 300SL work?
 

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Registered
1992 500SL
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13 Posts
Discussion Starter #20
I have found one on eBay that is supposedly from a '91 300SL it has a digital odometer. Mine is analog. That is what I was referring when I was talking about using a digital cluster. Are those interchangeable?
 
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