AMGAffalterbach

I've seen a lot of threads on this but all with slightly different symptoms or over SBC concerns. I was giving it gas on an off ramp the other day and I got a red battery warning in my center screen (no visit workshop or alternator warning, just a red batter) that, after restarting the car a few hours later, went away. Yesterday it came back each time I started the car but my HIDs were still working, didn't flicker, and sound system was running fine. Then, coming home from a party last night I got the COMAND "low battery voltage, shut off in 3 minutes" warning so I booked it home. The car is currently sitting in the garage and it isn't dead, but I'm thinking it could be the following since it's likely a charging issue:

Bad Fuse (according to a tech from MB Clinic)
Bad Battery (I don't think it's this since it was a spontaneous issue and it was load tested about a year ago)
Bad Alternator
Bad Voltage Regulator

I'm kind of scared to drive the car because I don't want to get stranded somewhere, but I can't really tell if it's a gradually draining battery that will leave me up sh*t creek, or a perpetual low-voltage state that is causing these warnings. Other than checking the fuses (not even sure which ones to check other than those next to the batter), how do I go about diagnosing the issue? Any advice would be greatly appreciated, I JUST finished repairing both front air struts and the car sat for a week and a half but it obviously isn't charging.

Finally, how much do alternators run for this car on average? What about AGM batteries? Thanks.

Plutoe

You may have a bad case of Columbian coffee fungus. I'm told the fungus has been creeping westward for years. I guess it's finally reached your great state.

I understand that the Cubans and the Colombians have partnered for a cure!

PSon't wet your pants, you do not have an alternator problem!! If you did their is a specific multifunction message---"Stop-Battery/Alternator, however I bet you do have an issue with electrical system and regrettably the quickest way to find the fault is via DAS Xentry--quick test--control mod view--- battery--???????? and yep the cause!!

AMGAffalterbach

Good to hear Plutoe, thanks! I have an appointment at 9:30am on Wednesday to get it looked at with Das Xentry and an appointment at 1pm on Wednesday to get the Columbian Coffee Fungus looked at by the doc.

boardboy330

I am having a similar problem. I have narrowed it to similar issues but in my research came across several posts about the passenger seat motor causing the issues. A bad relay leaving it run, and draining the batt after a few days.

Have you tried doing a slow charge on it til your appt? See if the symptoms go away or come back. Will help you narrow down if it's a battery or electrical system. Battery problems should come back immediately...but electrical system should stay away for a bit.

AMGAffalterbach

Interesting... yeah now I HAVE to do a slow charge on the battery over night tonight, I was driving home today (I had some vital work related stuff to take care of) and I got the warning after an hour of driving. Everything was fine until my ABS and ESP lights would flash for a second then turn off. Finally, ESP became inoperative, then COMAND shut off, then power steering started going as I was rushing off the highway, then airmatic adjustments shut off and the car became extremely stiff, and then as I was coasting into my driveway the car started losing power and died. It was a transient issue that just manifested in a drained battery over time.

The reason I know for sure it's not an alternator issue is that to make it home I had to keep it at high revs (3000k+) and the errors would go away since the alternator was sustaining the systems, but it eventually let go and luckily I stalled coasting into my garage.

AMGAffalterbach

By the way for your parasitic drains on the battery Boardboy I found this chart, also related to our issues from another MBWorld Thread:

boardboy330

That's fantastic, thank you. I know my 3rd brake light is out and has been for a little while now. I haven't had time to chase the lines and see why it's out. I installed a new LED bar and it's still not working. Maybe that error is causing the drain.

AMGAffalterbach

Yeah I would think a short in the system or something of the sort could be causing that parasitic loss, hooking it up to DAS Xentry would help boardboy, usually shows you if you have any open circuits anywhere.

As for me, I took the car into the shop this morning as planned (trickle charging over night gave me enough juice to get down there) and they narrowed it down to two things: bad voltage regulator or bad alternator. They're ordering in a new voltage regulator and they will test the systems from there, $160 isn't bad. A new alternator on the other hand is $1200 (I think he said you can get warrantied, rebuilt Mercedes ones for a lot less) so I'm hoping that's not it. A few threads on here have said it's usually not the alternator and the voltage regulator module is often the problem, so fingers are crossed. In an ML430 loaner meanwhile and barely surviving. Send help. I'm losing strength fast. Lol

SorryAboutThat

Any good things to report about the ML loaner...or was it a complete disappointment. Just out of curiosity, what was the fix for the problem you were having?

AMGAffalterbach

I can't believe I forgot to post the solution! It was the voltage regulator that was bad, not the alternator. $390 with labor, not as bad as it could have been. No issues since then and the car has been running very strong even with heavy load on the electronics. Interesting how the voltage regulator went out all of a sudden on the highway, but as another thread said on here the alternator is not often the issue.

As for the ML430 loaner, it was like the last ML - you can tell it wasn't Mercedes shining era of quality, a LOT of squeaks and rattles and definitely rode like a truck. I was kind of getting used to the high position on the road though, and the V8 in this ML was actually pretty strong I was surprised at the grunt it had. Not super fast but definitely had torque. NOTHING like the newer ML63 I've been in, that thing is incredible and so refined.

LILBENZ230

Okay I'm going to bring this back up. I have gotten just the red screen with the battery in it twice today. I put the car in dyno mode and the voltages seem low. Low-mid 12v range at idle. About 13.5-13.7 driving, though it will dip at times back into the 12s. At one point it was idling at about 12.0v and suddenly increased to 13.5v without me doing anything.

Autozone was nearby when I got the red screen, they said they load tested the battery and it was fully charged. VR failed the test, so did alternator. Thinking a bad VR could cause both it and the alternator to fail. The screen on the test machine showed 13.1v at idle.

VMI shows my cars alternator was replaced in the mid 40k mile range. Currently have 66k.

I am not a happy camper. Once I can't depend on a car to get me somewhere, the honeymoon is over.

LILBENZ230

I am unable to locate a part number for a VR on my 2009 E350.. can anyone help?

Plutoe

To do it correctly you need the VIN

LILBENZ230

If I were to give you the VIN, could you find it out? I have a Mac and EPC does not work.

Plutoe

Hey I am not looking for a date just trying to solve your issue----If you want help from me, and for me to be correct I need the VIN---the rest is up to you!!

LILBENZ230

WDBUF56X4984432589

I appreciate it!

Plutoe

Ah come on--VIN's have 17 positions---your response has 18 and then are not in the correct order---let me ask again---what is you VIN??

AMGAffalterbach

If your VR fails the test your alternator likely as well: try replacing it before you replace your alternator (which isn't as likely to go bad) and see if it solves the charging issue, if not then you have to replace both. I'm trying to save you money here lol

konigstiger

LILBENZ230

Thank you for all the help. Sorry, I have been without a computer and was trying to do stuff from my phone. The part is ordered.