Red Battery Light - Stumped
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Joined: Jul 2024
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2006 e350
Red Battery Light - Stumped
So I have a 2006 E350 4matic (05/2005 build - 272 engine) and I recently got the red battery light. The car previously sat for about 2 months because of blown rear suspension bags. The red battery light came up after replacing the bags.
Things I have done so far after searching the forums:
swapped voltage regulator (old one looked burned and the main pins looked real short)
swapped BCM - had a spare laying around
swapped central gateway
swapped aux battery relay
swapped AC control unit
checked BCM CAN wires (connector pins looked corroded so I replaced the connector since I had a spare)
checked BCM harness and cleaned each pin
charged batteries - both batteries are less than 1 yr old
checked all fuses - none were burnt out that I could see and test with a multimeter
After all that I am still getting the red battery light. Interior lights and headlights start flashing, ambient air temp sensor reads 185, window switches do not respond, etc. I checked using an autel and the codes I get are 9055, 9092, 9000, 2069, 1293, 1437, 0365, 0485. All of these codes seem random to me because once I let the car sit for a day with the BCM unplugged or the batteries removed all codes go away. I can start the car once, go on a 20 or 30 mile drive and the only thing I could notice is that the re-circulation light on the AC would start flashing. Once I turn off the car and turn it back on, the red light comes up. I lose communication with the BCM, and all these codes pop up,
Using the Autel I did a generator load test and it passed with no issues. When the car is at idle the voltage is around 13.8 to 14.0 according to the autel. Once moving the voltage is 14.1 On the cluster the voltage is at 14.0.
The only thing I can think of is to check grounds but not sure which ones to check. Not sure if this is relevant but when I was doing the voltage regulator I noticed that there was a 2 pin connector that only had 1 wire, not sure if there were supposed to be 2 wires or not.
At this point I am completely stumped. I have no clue where to even go and/or look at.
Things I have done so far after searching the forums:
swapped voltage regulator (old one looked burned and the main pins looked real short)
swapped BCM - had a spare laying around
swapped central gateway
swapped aux battery relay
swapped AC control unit
checked BCM CAN wires (connector pins looked corroded so I replaced the connector since I had a spare)
checked BCM harness and cleaned each pin
charged batteries - both batteries are less than 1 yr old
checked all fuses - none were burnt out that I could see and test with a multimeter
After all that I am still getting the red battery light. Interior lights and headlights start flashing, ambient air temp sensor reads 185, window switches do not respond, etc. I checked using an autel and the codes I get are 9055, 9092, 9000, 2069, 1293, 1437, 0365, 0485. All of these codes seem random to me because once I let the car sit for a day with the BCM unplugged or the batteries removed all codes go away. I can start the car once, go on a 20 or 30 mile drive and the only thing I could notice is that the re-circulation light on the AC would start flashing. Once I turn off the car and turn it back on, the red light comes up. I lose communication with the BCM, and all these codes pop up,
Using the Autel I did a generator load test and it passed with no issues. When the car is at idle the voltage is around 13.8 to 14.0 according to the autel. Once moving the voltage is 14.1 On the cluster the voltage is at 14.0.
The only thing I can think of is to check grounds but not sure which ones to check. Not sure if this is relevant but when I was doing the voltage regulator I noticed that there was a 2 pin connector that only had 1 wire, not sure if there were supposed to be 2 wires or not.
At this point I am completely stumped. I have no clue where to even go and/or look at.
Out Of Control!!
Joined: Apr 2019
Posts: 12,191
Likes: 6,889
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
tips
You have covered a lot of good maintenance.
Now we want reliability back for your car to stop quitting.
> The one GND everyone is invited to clean and double-up IS THE MAIN GND STRAP. (W212 has it all the way down low near tranny/exhaust).
> GND is a qualified provider of Mercedes troubles. Specifically those GND posts at front L/R footwell that can get soaked.
> Please translate fault code in english and cover whole car for CAN issues.
> Next I would go read data stream from ECU, BCM not expecting codes for everything important.
What would help focus is to understand the conditions that trigger the fault you're after...
✌️
Now we want reliability back for your car to stop quitting.
> The one GND everyone is invited to clean and double-up IS THE MAIN GND STRAP. (W212 has it all the way down low near tranny/exhaust).
> GND is a qualified provider of Mercedes troubles. Specifically those GND posts at front L/R footwell that can get soaked.
> Please translate fault code in english and cover whole car for CAN issues.
> Next I would go read data stream from ECU, BCM not expecting codes for everything important.
What would help focus is to understand the conditions that trigger the fault you're after...
✌️
Last edited by CaliBenzDriver; Jul 28, 2024 at 09:32 PM.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,550
From: MA
2008 E350 4Matic, 2011 E350 4matic
I think you should have just replaced the alternator. How many miles? Also you can have the voltage in the display while driving. What's the voltage when all this stuff happens? With the engine off but the car on, switch to the temperature display, hit the reset button 3 times and you should get the voltage display. 14.1 is a little low while driving, normally 14.5. So either bad regulator or alternator.
