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Silver 2010 S550
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257 Posts
Discussion Starter #1
My 2000 S430 has 103k miles on it. Over the past month I've noticed it cranking slower and slower especially if it hasn't been used for a day or two.
I recently left the car at the airport for 4 days while on a trip. Upon return it cranked very slowly but turned over. The next day I went to start it first thing in the morning and it just cranked slowly and no turnover. The battery also seemed to be draining as the cluster was going more and more dim. Eventually the thing jsut completely died and no crank no turnover no lights no nothing. Just a big German paperweight. Before it died completely I was sure to put the car into neutral so I could at least push it and steer it onto a flatbed. Had it towed to the shop and waiting for them to diagnose.


I thought it may be the CPS but from what I've read that seems to be more an issue when the car is warm. Also I couldn't understand why I got the big drain. My battery and plugs were replaced about 6 months ago. I'm at a loss and probably a loss of money when the shop calls. Any ideas what I can expect? :mad:
 

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2000 MB S500 and a 2009 Kia Optima
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63 Posts
It could be as simple as a warranty bad battery. But it could also be one of "those" electrical problems... they take forever to find, and no time at all to fix. If you get lucky, it will be a problem with a component that the Diagnostic system can pick up, and not a short deep inside some large wiring harness. Sorry to be the possible bearer of bad news, but you need to be ready for it.

I once trouble shot a charging problem, where the unit would stop charging but all the components checked out as being good. Turned out to be a broken wire inside the insulation, that reconnected every time I pulled the plug. So when I would test the wire it would check good. Then vibration would cause the short to open back up over the course of 50 miles or so and it would stop charging again. I found it when I got lucky and grabbed the wire in just the right place and felt the break.
 

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Current 2017 GLE350, 2007 S550, 2002 S430, 1998 ML320 Deceased 74 240D, 92 400E, 97 E420, 13 GLK350
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1,915 Posts
I looked for the root cause of a slow battery drain for quite awhile. After isolating the problem, made the attached troubleshooting guide to help others based on lessons learned, WIS, and advice from the forum. Good Luck :thumbsup:
 

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'02 CL500
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376 Posts
Before getting to involved with troubleshooting, I would have started by having the battery tested. It could have been bad and just needed replacement. This could be your only problem. If the battery is okay, then have the charging system checked. If its output is okay, then look at battery drain problems. You really should have started checking things out at the first sign of the problem. Your car was trying to tell you something. Good luck.
 

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2013 s550
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18 Posts
after a year of trying to figure my slow battery problem, i took it to the dealer, and it was the rear bus, located under the seat,$850 and its fixed.
 
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