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  #1  
Old 04-03-2013, 11:09 AM
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Join Date: Aug 2008
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Need some advice re: tach and speedo failure

Hey guys, I need some advice. '95 SL500, my tach and speedo quit immediately after replacing the battery this weekend. Everything else on the dash works. The MPG gauge is functioning, the odometer and trip odometer work, The cruise control works and the convertible top system works. All of the major wiring systems I replaced several years ago including the ETA rebuild by BBA Reman. All fuses have been checked and are OK and wiring to the battery seems OK. I had to jump the car to start it and had AutoZone swap the battery, the car wires were attached to the "old" battery at the time of the jump start, I also tried charging the battery before that and the wires were attached to the battery when I did this. I've done this before with no bad results. What happened?

What have I missed? Is there a signal generator for the tach and speedo, a relay or something else I've failed to check? I don't know how to remove the cluster, so I'm also open to suggestions on that too.

Thanks, Steve
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  #2  
Old 04-03-2013, 11:57 AM
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Join Date: Mar 2003
Location: Milwaukee Wisconsin
Posts: 1,149
The cluster is operated by a computer circuit.
Check this thread.
http://www.peachparts.com/shopforum/sl-forum/231273-hi-everyone.html

There is a voltage regulator that reduces the voltage from 12V to the required voltages for the computer chips. If this failed due to a power surge
when jumping or replacing the battery, the cluster will need to go in for repairs. There are a couple of shops that have been mentioned in other threads which do this repair work. I had been under the impression that the OVP was supposed to protect the cluster electronics as well as other computer circuits, but I've read in the other forum that it doesn't. I don't have a diagram, so I really don't know which is true. The cluster isn't difficult to remove. Just be sure to lower the steering wheel before you disconnect the battery. There are no screws and the connectors just unplug.
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  #3  
Old 04-03-2013, 02:25 PM
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Thanks Tecqboy, I've decided to pull the cluster. I've read all of the links you've provided, but none of them refer to a rather unique problem I'm having which involves just the speedo and the tach. Most of the other posts have referred to the problem involving intermittent flashing of dash lights involving turnsignals and mirror lights or brake lights. Nothing flashes on mine and the alternator is putting out the way that it should.

I used BBA Reman for my ETA several years ago, and they will evaluate my cluster for $35 if its non-repairable and $165 if it can be fixed. I don't think the bad capacitor mentioned in some of the posts is my problem because only part of the dash, the two related components, are out and everything else works normally.

Thanks, I'll post when I have a solution.

Steve
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  #4  
Old 04-09-2013, 04:00 PM
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Join Date: Aug 2008
Posts: 212
Wink speedo and tach failure SL500 '95

BBA Reman diagnosed my speedo and tach to have a failed microprocessor and not repairable by them at least. The speedo and tach would work for a while on their bench but than shut-down. Everything else on my dash worked perfectly. Go figure!!

All was not lost, as it turned out, I had a digital odometer/dash cluster and received a call from "Sam" who happened to have two clusters. One was pristine and worked perfect. I also found a drivers' side door panel in excellent condition. Both for $200 installed. Everything is working and the SL500 is now for sale and the ads will start on Autotrader and Craigslist and my local paper.

Steve
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  #5  
Old 04-09-2013, 04:38 PM
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Join Date: Mar 2003
Location: Milwaukee Wisconsin
Posts: 1,149
Just wondering....How does a company which specialises in re-manufactured VDO's not be able to replace the processor? Like, what else goes wrong in these things besides the electronic components? Well, you solved your problem and are moving on. It sounds like your car has been a nightmare of endless problems. I'm convinced it costs more $ to keep an old car running than to own a newer model, especially these R129's, which were produced in limited quantity and are too complex for good reliability as they age. I haven't had nearly as many "issues" as you, but I must admit that some rather unusual things have failed; parts most other cars don't even have. I can't believe that the original owner of my 300SL paid over $100K back in 1991. I have the original purchase agreement. Good luck on your next vehicle. Tod
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  #6  
Old 04-10-2013, 09:01 AM
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I have the original sales invoice for mine too and it exceeded $100K. I would in normal circumstances keep this since soo much as been replaced. But I found this mint Audi A4 Cabriolet that is 8 yrs younger with 40K less miles and I thought with the price of gas, it might cost less in the long run to operate. If I sell the MBZ, I'm OK but if it doesn't sell, I'll have to part with the Audi. My wife said one or the other but not both. On the Benz, if I hadn't found a donor '97 SL several years ago, I could not have been able to replace as many parts and resold what I didn't use to more than break-even. My labor was the least cost element of ownership. Anyway, we'll see where this takes me.

Steve
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