Mercedes Alternator function

Maynard Technician Ontario Posted   Latest  
Updated
Electrical
2004 Mercedes-Benz E500 4Matic 5.0L (113.969) 5-spd (722.6) — WDBUF83J04X112828
Alternator Will Nt Charge

Looking for alternator description of operation. Auxiliary battery in the car has been replaced as it was in very bad shape and consumer shutoff codes stage 1 and 2, 9051,9050. Now alternator does not come alive.

This alternator has Main battery cable connected to it and alternator case ground. There is 2 more circuits going to it, one from SAM module and one from PCM. 

Can someone direct me in testing this? I am not familiar on what should be expected on these two circuits from modules SAM and PCM.

Also is there any specific resets that should be down after a battery replacement and so on. 

Does Mercedes supply this type of info on a subscription type website?

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Joel Diagnostician
California
Joel
 

I am looking at the wiring diagram , seems to me like on pin 1 at the alternator should have positive voltage feed to regulator, pin 2 should hav some pulse width modulated signal.

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Dan Owner
Ohio
Dan
 

Morning. Hook up your scan tool and access Charging system Diagnosis. Take a look around what's going on. Here's a link to Dan's video explaining LIN Bus: youtu​.​be/tkaD_jomweA Good Luck, Dan @GEAR

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Marty Technician
California
Marty
 

Check for voltage at blue wire, circuit 61. Hope this helps, see attached.

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Michael Owner/Technician
Georgia
Michael
 

I don't have a diagram to give you specifics. There should be 3 wires going to the alternator. The one from the SAM should be power. There should be a ground and a signal wire from the PCM. The PCM will send the signal through the LINBUS which you should be able to see if you have a scope. You should do a full scan to see what codes there are and sort those out. Most likely an alternator…

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Tim Technician
Indiana
Tim
 

I have replaced many pcm's for losing the ability to control the alternator. Scope the pcm wire if it is dead then there you go.

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Dave Owner/Technician
California
Dave
 

Blue wire to SAM is circuit 61, tells car alternator is charging or not (sometimes doesn't illuminate cluster MIL when it should…) Blue / white wire is LIN buss from engine module. LIN signal modulates charge rate to do things like reduce charge rate just after engine start to lessen load on belt, or at full throttle to reduce engine load. LIN signal only reduces charge rate. Alternator will…

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Maynard Technician
Ontario
Maynard
 

Dave Thank you so much for the detailed explanation. That circuit 61 has me concerned, we have no voltage on it when key is on or car running. The limited written information I find about it hints that there should be battery voltage coming to the alternator from SAM. You have excellently written the operation which indicates the alternator is what supplies voltage to the SAM once the alternator…

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Marty Technician
California
Marty
   

No, will not charge with 2 wire connector disconnected. What values are you seeing on the Blue wire? plugged in and disconnected…running and KOEO? ME sends 12V on LIN bus, Blue/white wire (scope if voltage low), the alt (blue wire circuit 61) sends back 12 (or charging voltage) to the front sam.

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Maynard Technician
Ontario
Maynard
 

Blue wire plugged in is 0v all the time. I do not know what it is with it disconnected. Lin bus wire is at 12v. I have been doing alot of reading and this car appears to fall into the category of not being externally controlled. Not BSS or LIN controlled…. I am not experienced with these at all. But apparently there is options on these. Some are BSS controlled some are LIN and some have no…

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Dave Owner/Technician
California
Dave
 

On a closer look at the MB WebETM the 211 with M113 does not have interface (BSS or LIN). The blue wire to SAM is described as Alternator operation signal and is supposed to have 12v at idle. The Blue / white wire to engine module is described as Circuit 61 signal input (to SAM) and is supposed to have 12v with engine running. The document John Tirch referrenced verifies that regulator is…

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Maynard Technician
Ontario
Maynard
 

Thank you for chiming in again Dave. With engine running there is 12 v on circuit going to engine control module. I dont know if the alternator or the ECM is generating that. The blue wire to SAM stays 0v. So if it is supposed go to 12v at idle…. Is the alternator supplying that or SAM? As Marty indicated the SAM may be supposed to output a 12v signal. But then is it the alternators job to pull…

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Dave Owner/Technician
California
Dave
 

The closest car I have here now is a 2004 SLK 230 which only has the blue circuit 61 wire and a Valeo alternator. It charges with the plug off and there is power on the disconnected wire… Go figure. I've replaced a couple of 203 front SAMs that would not turn off the charge warning even though there was power at the blue wire.

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Maynard Technician
Ontario
Maynard
 

Ok! well that is pretty cool. Our car has both wires on it but what they hey. I think we have to go ahead with a regulator/alternator. I wonder if our car is grounding out the circuit then, We should also test it open. Our alternator does not say bosch or valeo, I suppose some off brand must have been installed at one time.

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Marty Technician
California
Marty
 

Dave, I suppose I spoke too soon regarding the confirmation if disconnecting plug. I forgot which engine this 211 had in it…so No, I cannot confirm disconnecting charge status. :-(, I will repost the next chance I get to give a definitive answer… Maynard, yes, this does have the conventional charging system alt, yet the blue wire should have voltage and since it does not, I would be looking at…

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Maynard Technician
Ontario
Maynard
 

Thank you Marty, My main concern was to understand what needs to be present in order to get some output from the alternator….. at this point with all of your participation it appears as tho the alternator should have at least some output regardless of the status of the blue and blue/white wires. The alternator does not charge at all right now. Fine tune control may still be in question after…

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Marty Technician
California
Marty
 

I found this explanation in a different forum regarding similar condition, Although this is a M113K, I believe it is comparable, perhaps it will provide some clarity: "I hope this well help someone...ok the car came in from another shop and the owner had installed his own alternator. I had swapped front sam into a cls500 and the old one would not charge. I put a new sam into the 55 amg and…

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Maynard Technician
Ontario
Maynard
 

AHA! Ooooo thats great Marty! So at that rate, we seem to have 12 volts on the wire from ME but nothing going to SAM, and alternator is not charging at all. That is perfect!

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Maynard Technician
Ontario
Maynard Update
 

Thank you every one for the tips and documentation etc. We have 12 volts on our LIN line and nothing at all on the Wire going to SAM. So we will need to do something with the alternator. Very grateful for the tips

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Dan Owner
Ohio
Dan
 

Maynard, What happens when you power up circuit 61 blue wire? It should start charging! Look at your dashboard does the charge indicator come on with the IGN on? I don't have ETM at home so I can't give you precise info but power up the blue and report back. Dan @ GEAR

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Maynard Technician
Ontario
Maynard
 

Thank you Dan, When the blue wire was powered up the alternator still did not charge. Thank you for that thought, we were also thinking this should get it going but when it did not alot more questions came in.

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John Technician
Utah
John
 

Gf15.40-p-2000a. All data has this document

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Caleb Diagnostician
Indiana
Caleb
 

Thanks for this post Marty. I have and 06 CLS500 in here this morning not charging. This post was the quickest way for me to get accurate description and operation for this 2 wire.

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Marty Technician
California
Marty
 

You're welcome. Happy to know the efforts and information on DN are being used as a resource for diagnostic strategies.

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