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'02 ML500. 22A292576
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232 Posts
Discussion Starter #1
For about a month, my battery light has been coming on intermittently. Usually at idle, usually when cold, but it's becoming more frequent. It did it the other day on a long downhill run into LA.
When it first started happening, I checked the charge (12.75V) and the charging rate (13.85V). Seemed OK. I had the battery load tested and the battery place said it needed replacement so I did.
The problem persists with the new battery. I'm suspecting bad belt (seems fine) or spotty alternator. Any ML quirks I'm not aware of? Any other ideas?
 

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Premium Member
02 ML320 06 ML500
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17,105 Posts
You probably need to replace your voltage regulator on the alternator. Very easy to do, just remove the back cover and it is right there on the rear. If you don't do it yourself, the dealer or an indy mechanic will sell you the entire alternator.
 

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'02 ML500. 22A292576
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232 Posts
Discussion Starter #3
Thanks, just the info I was looking for. I seriously doubt the alternator is bad. I've never had one work intermittently before. Either works, or dies.
 

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ML 270CDI 2002, BMW K1300S, VW POLO 1.9TDI
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515 Posts
You might only need a new alternator 'brush set' (sometimes called slip ring brushes), they wear down during their life and might not be in firm contact with the slip ring. check the brushes out first before spending more money.
 

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'02 ML500. 22A292576
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232 Posts
Discussion Starter #6 (Edited)
Brushes come with voltage regulator.

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That's good news. Although I saw nothing to that effect on the website when I ordered the part from Pelican yesterday. I'll see when the part arrives*.

FWIW, the way the problem is intermittent, and the fact that my alternator seems to be working perfectly, leads me to believe it's an electronic part on it's way out (i.e. regulator) as opposed to a physical/wear issue (brushes). My WAG would be that brushes would manifest as continually lower output. Mine is still in the 13.75V-14.25V spec.


*DOH! The picture just loaded. I see the brushes now, and that is indeed the part I ordered. It was a small drawing though didn't clearly show the brushes.
 

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'02 ML500. 22A292576
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232 Posts
Discussion Starter #7
btw, Does anyone know of a source for the wire clips like #44 in the diagram above? In my experience, they harden and crack every time you try to undo one. I have several on my ML and my Porches that need replacing and I've never been able to find a source for them. IME, if the dealer even can get them, they are prohibitively expensive. I've never seen them in a WURTH or Au-Ve-Co catalog.
 
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