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  #1  
Old 03-21-2021, 06:33 PM
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Gauge Cluster Issues

While troubleshooting a different problem, I had my gauge cluster out and apart. I've put it back together wrong, apparently. New issues: Gauge lights don't work. Fuel gauge pegs at full on startup, and temp gauge goes to full within a minute or two of starting. High beam indicator stays on. Other info: The rheostat has a jumper soldered across it. There is also a jumper from the rheostat to the #3 pin on the round electrical connector to work around a bit of the PCB that flaked off years ago. I originally installed it years ago, and it came off as I was pulling the cluster. I got Pin 3 based off a post I saw on this site, but I'm not sure that's correct.

What did I do wrong?

Edit: The patient is the '83 300D in my signature.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Last edited by Skippy; 03-21-2021 at 10:56 PM.
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  #2  
Old 03-22-2021, 03:38 AM
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You may have put the 15 pin plug in wrong and shorted some stuff. It's a keyed plug, but it does happen. Or your ground might be wonky now after this last cluster R&R and may need a new ground cable from the cluster to the ground behind the dash.
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  #3  
Old 03-23-2021, 12:37 AM
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I'd consider having the keyed connector in wrong unlikely. However, the ground thing sounds quite plausible. What are some good places to connect an auxiliary ground?
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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
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  #4  
Old 03-23-2021, 12:41 AM
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Post Proper Grounding

Use an part of the body, use a star typ lock washer under the nut and ring lead .

German cars use brown wire for grounds .
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1982 240D 408,XXX miles
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  #5  
Old 03-23-2021, 06:24 AM
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I have seen where the keyed part of the plug had broken off making it very easy to misalign the connector.
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Old 03-23-2021, 12:06 PM
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Quote:
Originally Posted by MS Fowler View Post
I have seen where the keyed part of the plug had broken off making it very easy to misalign the connector.
X2
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  #7  
Old 03-24-2021, 11:02 PM
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The D-shaped key was still there when I had it apart last, and I didn't have to use much force to get it in. We'll see when I take it apart this weekend. I do wonder how a ground issue could result in the high beam indicator being on, albeit too dimly to see it during the day.
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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
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  #8  
Old 03-25-2021, 01:41 AM
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One way to test out the cluster ground circuit is to use a long test cable. Connect one end to the battery grnd point the other end would go to the grnd point on the wiring harness. Using a continuity meter will verify the wiring harness grnd point to the cluster. If the key "D" shaped connector is still connected to the plug then I can't see how this would cause a problem.
MB's have a funky issue with with grnd circuits. In electricity devices will seek the least resistant path to ground and can take out other circuits in the process.
Please don't ask how I know this......
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  #9  
Old 03-26-2021, 08:29 AM
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multi plug

Any good .W123 diesel
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Gauge Cluster Issues-untitled-1.jpg  
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  #10  
Old 03-26-2021, 02:10 PM
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Post Poor Grounds & Current Backflow

" I do wonder how a ground issue could result in the high beam indicator being on, albeit too dimly to see it during the day."

It glows because the indicator lamp is providing a poor ground path .

Like the millions of old 50's & 60' GM products that have a dim taillight that goes out when you step on the brake : the secondary filament provides a ground path until you energize that circuit then the light goes out .

Auto electrics isn't rocket science, you just need to learn it by doing, you'll get this fixed ere long .
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1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better
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  #11  
Old 03-27-2021, 07:23 PM
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Quote:
Originally Posted by vwnate1 View Post
Use an part of the body, use a star typ lock washer under the nut and ring lead .

German cars use brown wire for grounds .
Where on the cluster?
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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
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  #12  
Old 03-27-2021, 11:20 PM
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Any screw on the speedometer.
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  #13  
Old 03-27-2021, 11:36 PM
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I'll try that.
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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
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  #14  
Old 03-28-2021, 02:59 AM
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Post Binnacle Ground Connection

I'd take a photo and post it if it wasn't so god damned difficult to do so, it used to be simple, now it's almost impossible to upload any attachments .
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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better
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  #15  
Old 03-28-2021, 07:04 PM
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Quote:
Originally Posted by Felching View Post
Any screw on the speedometer.
It seems to have worked. The fuel gauge is now reading a plausible value instead of pegging full. I'd take it for a test drive, but I'm going to walk over and grab a pambazo first. It will be a few hours before it's dark enough to tell if I fixed the dash lights. I may work on the Jag a little bit.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
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