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Discussion Starter · #1 · (Edited)
C240 Alternator Question

This morning about 20 minutes after start my '01 C240 displayed this message: Undervoltage Consumer Defective. Is that alternator related - perhaps the alternator is not supplying required power to the system? I also noted a noise coming from the passenger side of the engine when I start the car in the morning. Chirping short (and intermittent) noise, reminds me of the noise that waterpump bearing makes when busted. Has someone experienced something similar. Is the alternator removal an easy job?

Thank you.
 

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Discussion Starter · #3 ·
That what I am also suspecting, a voltage regulator. Do you know if it is possible to easily replace the regulator in this alternator like it was possible on 80's -90's model alternators?
 

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yes the regulator is easy to replace. you can do it with the alternator is the car. just remove the 2 torx bolts holding the alternator to the engine, turn it to the side and remove the small screws that hold the regulator to the back of the alternator.
 

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Discussion Starter · #5 ·
I'm having a problem locating just the voltage regulator, looks like everybody is only selling a remanufactured alternator for W203 ('01 C240). Anybody can advise where to try?
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Discussion Starter · #7 ·
Thanks. I have one more question. I measeured the battery and it has 12.44V. Could it be failing? And if it is a faulty alternator, is there a message saying so in the C?
 

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Discussion Starter · #9 ·
I did more testing, the voltage actualy drops to 11 V with the car running, so the alternator is the cause. I will remove the alternator to see how the voltage regulator looks - if I need to replace just the regularor or the whole thing. The car has 80k miles, what do you recommend?
 

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People laugh at me - but with no gauge (Shame on you M-B) I use this about once a month...it helps to keep an "eye on things"
Jake
 

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Discussion Starter · #11 ·
Update on my "Undervoltage Consumer" condition. Brought the alternator to the specialized automotive electrical shop, they tested it and it passed with flying colors. They were also skeptical that the battery could trickle the message. So right now I am really lost as to where to look next. Any suggestions?

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Discussion Starter · #13 ·
voltage regulator

I replaced the voltage regulator attached to the alternator and problem solved. For some reason, the alternator shop did not see the issue. Worry free motoring since (almost a year ago).
 

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2001 Mercedes-Benz E320 4Matic Wagon
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yes the regulator is easy to replace. you can do it with the alternator is the car. just remove the 2 torx bolts holding the alternator to the engine, turn it to the side and remove the small screws that hold the regulator to the back of the alternator.
Voltage regulator replacement procedure question: Are you saying that you do not have to unplug the alternator or disconnect the battery to replace the voltage regulator on a 2003 C240 4Matic (150 amp alternator)? Just remove belt, disconnect 2 torx bolts and replace voltage regulator while in the vehicle? It would be nice if I did not have to disconnect the battery and risk destroying the SAM. Thanks, Jeff
 

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Voltage regulator replacement procedure question: Are you saying that you do not have to unplug the alternator or disconnect the battery to replace the voltage regulator on a 2003 C240 4Matic (150 amp alternator)? Just remove belt, disconnect 2 torx bolts and replace voltage regulator while in the vehicle? It would be nice if I did not have to disconnect the battery and risk destroying the SAM. Thanks, Jeff
Here's a pic of the regulator and brushes from a Valeo 120A alternator.
It just bolts onto the the back.
I don't think it has any external connection.

But every alternator is different.
I ended up taking it out, and having it rebuilt by an electrical shop,
while just doing the brushes might be enough, this piece here is around 120 or more from MB and the whole rebuild, new regulator, diodes, brushes, bearings, and a general once over is typically less then $200.
Mine was 150.
 

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Voltage regulator replacement procedure question: Are you saying that you do not have to unplug the alternator or disconnect the battery to replace the voltage regulator on a 2003 C240 4Matic (150 amp alternator)? Just remove belt, disconnect 2 torx bolts and replace voltage regulator while in the vehicle? It would be nice if I did not have to disconnect the battery and risk destroying the SAM. Thanks, Jeff
If the engine is not running and the ignition is off, the regulator is just not doing anything. You should have no problem changing it out, but I do believe battery voltage is on one terminal so use insulated tools. If you want to change out the alternator, I would remove the battery negative cable, just like any other serious electrical work.
 

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Nice work bro!

I just removed my alternator and stumbled across this thread. After reading about your journey, I feel more confident about my problem.

at about 70K, My Seat Control Module went haywire a few years back and put a constant drain on my battery. After wasting time/$ on a new battery, a blown SAM unit, and other expensive parts, my car was finally back to normal. A few problems with blown tail lights here and there, but nothing too severe (For a Mercedes that is). I imagine my alternator went through quite a beating during that time.

At 180K+, my car started to make a weird noise at idle. It would only happen when I was in D and parked at a light or something. It was a random chirping noise (Like a cricket). Almost like the air being pushed out of a balloon slowly (Sorry, I don't know how else to describe the sound). It also came from the passenger side of my engine. It annoyed/worried me, but my car ran fine. I'm about a week away from changing my spark plugs so I figured I'd worry about it later.

So today as I gun it leaving work, a red warning light comes on in the instrument cluster. It says something like "Battery/Alternator check" or something. This begins to happen every time I gas the car. After a while, there is another alert. This time it is an orange alert saying something like "Under Voltage Consumer Defective". The first thing I think is that Mercedes rigged their cars to reject any aftermarket battery as a scheme to force everyone to buy expensive Mercedes Factory batteries. haha. The car was still running fine so I began to think it was the SAM or something (Sh*t). I made it to my exit 40 min later and I stopped to see if a restart would change anything. The car struggled to turn over this time. I went straight to Kragen and had the battery charged. They then checked the alternator and told me it started out as 14v, but when I turned on headlights, radio etc, it went down to 12v. I imagine that when I accelerated, it went down to 12v as well (or lower). The car ran smoothly, but felt weaker.

I just pulled the alternator from the car and I'm going to buy a refurbished alternator tomorrow morning. My local shop quoted me close to 100$ after a core exchange. I hope the alternator is what the problem is. After reading your story, I think it is.

I'll let you know how it goes. Thanks again man for the awesome info.

**UPDATE as of 2/5/10**

I changed the alternator on 8/1/09 and it fixed all the problems. As soon as I turned the car on, I noticed that the noise was gone, the warning lights were gone, and the car even seemed to be idling a bit smoother.

Here were my symptoms.
-Strange cricket chirping noise from passenger side in engine.
-"Battery/Alternator Check" warning light
-"Under Voltage Consumer Defective" warning light
-Electronics in vehicle flash on/off, pulsate, and act funny.
-Quick short hesitation in acceleration from dead stop.

Remedy.

-Replace Alternator (100$ with core exchange, or 260$ brand new)
It took about an hour to do and required pretty basic hand tools.
 

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This morning about 20 minutes after start my '01 C240 displayed this message: Under voltage Consumer Defective. Is that alternator related - perhaps the alternator is not supplying required power to the system? I also noted a noise coming from the passenger side of the engine when I start the car in the morning. Chirping short (and intermittent) noise, reminds me of the noise that waterpump bearing makes when busted. Has someone experienced something similar. Is the alternator removal an easy job?

Thank you.
I JUST finished doing my alternator in my C320. I had the same thing going on in mine. Weird noise for a week or two then, the under voltage problem and then it finally went.

It wasn't hard to remove mine, not the same as the 230's as they come out the bottom. I just read a really good how to on removal. (do a search for under voltage) But, I fired it up and all so far is fine. Doesn't take that long either. Just be sure to get the proper tools first as you'll need an inverted torx socket set.
 
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