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I have a 2004 Mercedes c230 kompressor sedan with just 66,000 miles on it . The last two days I have been getting the red battery /alternator light , last month the voltage was 12.9 ,now the voltage reads 11.7 , and if I turn the wipers or radio on the battery/alternator light comes on and keeps flashing . Is this the alternator or the voltage regulator ,or should I just change the alternator since it is connected to the voltage regulator ? Please help !!!!!
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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Welcome to the forum!

It's probably the voltage regulator which can be replaced as an individual part. Before doing that, check the belt to make make sure it's not slipping. In fact, I'd remove it and check the alternator pulley and the idler/tensioner pulleys to make sure they all spin freely. If that's all good, then I'd replace the voltage regulator.
 

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I have same battery alternator light come up at some point. I took the car for scanning and the alternator shows that it’s charging.
 

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Welcome to the forum!

It's probably the voltage regulator which can be replaced as an individual part. Before doing that, check the belt to make make sure it's not slipping. In fact, I'd remove it and check the alternator pulley and the idler/tensioner pulleys to make sure they all spin freely. If that's all good, then I'd replace the voltage regulator.
this is the most likely problem. another symptom is that the engine is sluggish and the gear shift is not smooth.
 

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CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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You need to put a voltmeter on it while you are driving the car. it should be fairly stable, 14v at idle. You should have somewhere in the range of 13.2v-14.2v when driving and electrical demands change. If you get anything outside of that range, it's most likely a bad voltage regulator.
 

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Discussion Starter #6
Welcome to the forum!

It's probably the voltage regulator which can be replaced as an individual part. Before doing that, check the belt to make make sure it's not slipping. In fact, I'd remove it and check the alternator pulley and the idler/tensioner pulleys to make sure they all spin freely. If that's all good, then I'd replace the voltage regulator.
thanks, I just went ahead and changed the whole alternator and it fixed the issue completely .
 
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