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  #1  
Old 12-07-2013, 06:55 AM
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Instrument Cluster Woes: WTB

Hey guys,

The radio on my 380sl started turning off again whenever I hit the brights, and sometimes even the brakes. So I re-soldered the post for the brown (ground) wire on the 4-wire connector behind the tach, since that cured the problem the last time I had it.

Well, it cured the problem this time, too. But when I went to put the windows down, they didn’t work, evidently because I neglected to disconnect the battery :-( , and something I did blew fuse 10 which powers the windows. So, I replaced that fuse, and now the windows work again.

However, now the fuel, temp, and oil pressure gauges, comprising the unit the EPC calls the Instrument Cluster, are completely dead — though the economy gauge and every other electronic thing on the car works fine.

After adding the extra ground wire that you guys suggested many times, the gauges still don’t work. So I’m concluding that whatever I did to blow the fuse must have fried something on the cluster, too. Consequently, I was wondering if anybody has ever tried repairing it.

Alternatively, I was hoping that someone here might have one they’d like to sell — though the EPC suggests that the cluster (PN: 0035409447) is unique to the following models: 280sl and slc; 380SL and SLC; 450slc and 500sl.

As this is my daily driver, any help would be greatly appreciated.
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1981 380SL
Chassis: R107.045
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  #2  
Old 12-07-2013, 07:26 AM
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Sounds more like the star connector on the back of the cluster is not on properly.
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  #3  
Old 12-07-2013, 07:34 AM
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Thanks for the quick reply, Pete. I was hoping that it was the star connector. So, I took it off and put it back several times, making sure it was seated each time. But it still doesn't work.

Any other suggstions?
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  #4  
Old 12-07-2013, 07:48 AM
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I have never heard of a cluster going bad, erratic, yes. You say all other lights work. Directionals, idiot lights ?, they are all on the star. Next I would test the star for power and ground and also jump the guages to see if they work.
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  #5  
Old 12-07-2013, 08:16 AM
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Thanks again for the quick reply, Pete, and for helping me trouble shoot this.

The searches I've been doing to find people who had the same problem and, hopefully, solved it definitely supports your observation that the clusters seldom go bad. In fact, I didn't find one message that dealt with a dead cluster. So, I still hoping it could be something simple.

However, after looking at the wiring diagram in the on-line manual, I can't figure out which pins on the star provide power or ground, or how to jump the gauges.

So, I'm hoping that maybe you or someone else could walk me through one or both of these tests?
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  #6  
Old 12-07-2013, 08:33 AM
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Do the directionals or idiot lights work ?
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  #7  
Old 12-07-2013, 08:48 AM
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Yep. Everything seems to be working. Except, now that I think about, I don't recall seeing the emergency brake light come on when I depressed the pedal. So I'll have to check that, though I'd really be surprised if that could have anything to do with it. Still, I guess it's worth trying.

Another thing that I noticed when I was looking for a used cluster is that the dimmer switch seems to be attached to the cluster. But I jumpered mine some time ago, and the lights it controls are still as bright as they've always been. So, I doubt that it's the dimmer switch.
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  #8  
Old 12-08-2013, 12:24 PM
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did you look closely at all the traces, sometimes they get a crack or get fried
and you are sure the star plug is on right , no bent /missing pins?

I do have one, I dont know the year , Ill get the part number off it , it is in spectacular condition
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  #9  
Old 12-08-2013, 01:48 PM
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I agree

Quote:
Originally Posted by meltedpanda View Post
did you look closely at all the traces, sometimes they get a crack or get fried
and you are sure the star plug is on right , no bent /missing pins?

I do have one, I dont know the year , Ill get the part number off it , it is in spectacular condition
Inspect the circuit traces for burn or cracking.
W123: Instrument cluster Printed Circuit Board repair


.
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  #10  
Old 12-08-2013, 02:46 PM
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mine is off a 74 so dont think it will help
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Ron
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #11  
Old 12-09-2013, 05:38 AM
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Quote:
Originally Posted by meltedpanda View Post
did you look closely at all the traces, sometimes they get a crack or get fried
and you are sure the star plug is on right , no bent /missing pins?
I haven't gotten up the guts to take the cluster out yet, since I don't want to make matters worse than they already are. So I don't know if any of the traces are fried. But I've removed and seated the star plug at least a dozen times now, and none of the pins are bent. Thanks for checking out the one you have. Too bad it's an earlier version
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  #12  
Old 12-09-2013, 05:43 AM
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Quote:
Originally Posted by whunter View Post
Inspect the circuit traces for burn or cracking.
W123: Instrument cluster Printed Circuit Board repair


.
Thanks very much for this link. It gives me a much better idea of how to approach the problem once I get the cluster out. I was looking for a thread like this but couldn't find one.
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  #13  
Old 12-09-2013, 12:40 PM
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Thanks again for the help, guys. After doing some more research -- which led me to a number of other very informative posts by the “usual suspects” -- I found the pin-out for (a) the star connector and (b) the 4 wires behind the speedo under Sec. 54-250 of the manual, “Removal and Installation of Instrument Cluster.” What a surprise!

However, an even greater surprise was that the diagram for the wiring behind the speedo in the attached picture didn’t match mine at all. More specifically, the 2 brown grounding wires on my speedo are on the bottom, left post. The black wire with the blue stripe -- which is hot and apparently feeds the instrument cluster through pin 2 on the star connector, is on the bottom right. The white wire that goes to the speedo is on the top left, and the green wire – which is also hot, and apparently goes to the defunct, 02 sensor light – is on the top right.

In contrast, the wiring diagram appears to have it upside down. The 2 brown grounding wires are on the top left, The hot black wire with the blue stripe is on the top right. The white speedo wire is on the bottom left, and the green/yellow wire to the 02 sensor indicator is on the bottom right.

Even though I was fairly certain that my wires were on correctly, and everything had always been working properly, I tried setting them up the way the diagram had it, which caused things to act erratically. Among those things was that my fuel gauge indicator pegged to the Full position, and stayed there even after I turned the car off, which led me to believe that maybe it was OK. However, it wouldn’t reliably repeat that behavior when I tried it a number of times afterwards. So, I’m still not sure what’s going on with it?

To eliminate the possibility that the brown grounding wires on the speedo were causing my problems, I disconnected them. Instead, I used only the extra ground wire I had attached between the grounding strip on the top, left corner of the speedo, and a bolt under the dash. When I attached the star connector to the instrument cluster everything - i.e., except for the cluster - worked as they did before -- ie.e, when the brown, ground wires were attached behind the speedo. So I know now that it’s not a ground wire fault, and that a good extra ground is all a person really needs to ground the system.

So, here’s where I’m at now: on my way to Radio Shack to get the fiberglass, abrasive pen and the conductive pen in the post that WHunter linked to, as that explains how to repair burnt traces.

Before I actually take everything apart though, I was wondering if anyone could tell me how to try jumpering the pins for the fuel, pressure, and temperature gauges on back of the cluster? I know that pin 2 and, if I recall correctly, pin 12 in the cluster are hot. But I’m not really sure how to use either of those to try jumpering the gauges?

Thanks very much again for the help you guys have given me, as it has been invaluable
Attached Thumbnails
Instrument Cluster Woes: WTB-star-connector.jpg   Instrument Cluster Woes: WTB-speedo-wires.jpg  
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  #14  
Old 12-09-2013, 01:23 PM
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FYI

I suggest re-titling and moving this thread to the correct forum.


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Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Prototype Vehicle build.
Prototype Fleet Durability
Prototype vehicle instrumentation.
Technical Quality Auditor.
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1978 280SE
1980 240D
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  #15  
Old 12-09-2013, 01:50 PM
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I re read the first post, so you tied into the ground that feed the panel? And something you did blew a fuse?
Hmm so if the pod is orginal , worked until you did what you did, you either altered or shorted the wire bundle or fried a trace
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99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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