Instrument Cluster W211 320cdi

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MBV6

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Joined
Dec 20, 2023
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5
Location
Northern Ireland
Car
2009 320CDi Sport
Just thought I'd share..was having bother after a flat battery, even after charging the battery overnight the instrument cluster wouldn't come on and was planning on changing it..so driving to work with the wireless OBD2 plugged in so I had the dash for speed etc and it showed the battery voltage...the very second it hit 13.3V from 13.2V the cluster sprung to life! I had changed fuses, unplugged battery, took it out for an entire night, read through the forums for cluster faults etc thinking surely it should work while attached the charger but nope it didn't just until it got enough charge to peak over 13.2V...moral of the story a dying battery can look like SAM problems or a cluster problem on these older wagons... new battery on the way!
 

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13.3 volts is very low for a running engine unless it has a ‘smart’ charging system.
Keep an eye on it and check that it goes above 14 for a good part of the journey 👍🏻👍🏻👍🏻
 
13.3 volts is very low for a running engine unless it has a ‘smart’ charging system.
Keep an eye on it and check that it goes above 14 for a good part of the journey 👍🏻👍🏻👍🏻
I doubt it's smart, I reckon the battery is just knackered, new one on it's way this evening hopefully reads better once it's in! - Thanks
 
I should still be showing a higher voltage than that with the engine running....dead battery or not....its the charging voltage you are seeing not the battery voltage....14v min.
 
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I should still be showing a higher voltage than that with the engine running....dead battery or not....its the charging voltage you are seeing not the battery voltage....14v min.
Yes I get you...you think alternator not pulling its weight??..
 
Or maybe I do have a smart charging alternator? I read about alternators that drop down below 13V when the battery is over 80%?
 
I think your alternator is on its way out… with the running engine, it should be around 14V.
 
If it’s a smart system, you can see anything from the high twelves to the low fifteens, depending on how well charged the battery is, what you are doing - acceleration has the lower voltage, deceleration the higher. Problem is, it’s software driven so different models and makes will act differently.
Non ‘smart’ systems are much simpler. You should see around 14.1-14.5 with the engine running.
Whatever, 13.3 does look too low, and sounds like the alternator (or regulator) may be faulty.
 

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