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I keep getting the error in the title pop up. It will then disappear after idling for a while. However today was the first time that it happened on a long drive, where the alternator should be charging it up. The alternator is charging it back up at idle but the IB value looks low to me.
I accessed the "secret" menu and have attached the picture of the readings. This is at idle.
Ib-1 amp - is this low or roughly correct? Does this indicate a new alternator is needed?
I assume if this is low then it's potentially
Battery is less than a year old
Last edited by Rhornett92; Jan 21, 2025 at 01:13 PM.
Reason: Picture in wrong place
I never heard of that message before so had to look it up.
You say the battery is fairly new, double check to make sure the correct one is installed. Verify the age of the battery, should be stamped on the negative post.
Double check the clamps are on tight to the battery posts.
Scan with a Mercedes specific obd scanner for any faults. I sometimes see a stored fault for the alternator output, its not an issue in my case just pointing out a scanner may point you in the right direction.
Seeing that 14.7v it does look like the alternator is working and charging. I think if the alternator were not charging, or working intermittently you would see a red battery warning pop up on the dash. Im speculating.
It’s possibly worn alternator brushes or a failing regulator. This warning is triggered when system voltage drops below 11.8 V for more than a few seconds on 204 models. 2017 Estate may be an S205, but it should be similar. When testing the alternator, do it at idle and also at 2000-2500 RPM. That warning may also create a diagnostic code. Have you scanned for any DTCs?
It’s possibly worn alternator brushes or a failing regulator. This warning is triggered when system voltage drops below 11.8 V for more than a few seconds on 204 models. 2017 Estate may be an S205, but it should be similar. When testing the alternator, do it at idle and also at 2000-2500 RPM. That warning may also create a diagnostic code. Have you scanned for any DTCs?
I'm roughly 70 miles from home due to work, so not with my scanner or usual tools unfortunately. Trying to figure out if I risk the journey back tomorrow and worse comes to worse get recovered, or if I pay through the nose at a garage before I leave tomorrow.
Is the battery correct as specified, meaning you didn't put a new battery in that was a different specification?
Your voltage seems a little high, but not out of range. You should get the alternator tested.
What should the IB amps be roughly when driving. I drove with the stats up this morning and it looks as though all is fine whilst moving, however when stopped, it's not generating enough power for all the electrics that are on. Heated seats, standard entertainment system and heating. Which is then causing the voltage to drop.
I keep getting the error in the title pop up. It will then disappear after idling for a while. However today was the first time that it happened on a long drive, where the alternator should be charging it up. The alternator is charging it back up at idle but the IB value looks low to me.
I accessed the "secret" menu and have attached the picture of the readings. This is at idle.
Ib-1 amp - is this low or roughly correct? Does this indicate a new alternator is needed?
It is strange actually a bad aux battery might also trigger the same warning, but usually it will say aux battery malfunction instead, there were still cases that a bad aux battery triggers the stop vehicle leave engine running message though. MBs are very particular when it comes to voltage and very sensitive to voltage changes.
It is strange actually a bad aux battery might also trigger the same warning, but usually it will say aux battery malfunction instead, there were still cases that a bad aux battery triggers the stop vehicle leave engine running message though. MBs are very particular when it comes to voltage and very sensitive to voltage changes.
Had the battery and the charging system checked at Kwik fit today and they report all is fine. Was fine on my drive home today, however since then I've done 2 smaller journeys and the warning has reappeared. I'm now stumped!
Had the battery and the charging system checked at Kwik fit today and they report all is fine. Was fine on my drive home today, however since then I've done 2 smaller journeys and the warning has reappeared. I'm now stumped!
Hmmm, I am guessing the XENTRY TIPS document wasn't helpful at all?
Hmmm, I am guessing the XENTRY TIPS document wasn't helpful at all?
I checked and both look okay, no overlapping or glue on contacts.
I charged the battery yesterday and got it to 12.4v, over night this is now back to 12.2 and has a consistent IB of -8/-9, at stand still no engine running, just the display for the read out. This seems like allot of drain for nothing being on. Could I have a parasitic drain somewhere?
I checked and both look okay, no overlapping or glue on contacts.
I charged the battery yesterday and got it to 12.4v, over night this is now back to 12.2 and has a consistent IB of -8/-9, at stand still no engine running, just the display for the read out. This seems like allot of drain for nothing being on. Could I have a parasitic drain somewhere?
I checked and both look okay, no overlapping or glue on contacts.
I charged the battery yesterday and got it to 12.4v, over night this is now back to 12.2 and has a consistent IB of -8/-9, at stand still no engine running, just the display for the read out. This seems like allot of drain for nothing being on. Could I have a parasitic drain somewhere?
That may be too much. About 3A runs the ECU. Then some more for the ventilation system which is never really off if you’re in the car and looking at the display. Maybe some more for the DAS components like ESL, EIS, TCU, etc. Your alternator covers that and more because it recovers at idle.
To really see if there is parasitic draw, current needs to be measured with a meter about 15 minutes after being parked, doors closed, and the key out of range of the car. Unless the car has gone to sleep, the draw will still be high, with ECU off standby, ventilation system active, seat sensors active, DAS waiting for input. It’s difficult to troubleshoot because if you walk out to the car with the key and open the door, the car’s kinda like, “Hi, mom/dad. Can we play Barbies?” And like a kid, it won’t stop until you leave it alone and it gets bored and goes to sleep.
But your warning isn’t due to parasites. It’s from the system voltage dropping too low while running. You have a hidden problem that we haven’t been able to help you find yet. It has to be in the system that manages the alternator or battery at driving speeds. Your battery is appropriate and your alternator tests good. The battery sensor is on the negative battery cable. Maybe there? Or the battery control module (BCM). I’m just throwing out guesses.
That may be too much. About 3A runs the ECU. Then some more for the ventilation system which is never really off if you’re in the car and looking at the display. Maybe some more for the DAS components like ESL, EIS, TCU, etc. Your alternator covers that and more because it recovers at idle.
To really see if there is parasitic draw, current needs to be measured with a meter about 15 minutes after being parked, doors closed, and the key out of range of the car. Unless the car has gone to sleep, the draw will still be high, with ECU off standby, ventilation system active, seat sensors active, DAS waiting for input. It’s difficult to troubleshoot because if you walk out to the car with the key and open the door, the car’s kinda like, “Hi, mom/dad. Can we play Barbies?” And like a kid, it won’t stop until you leave it alone and it gets bored and goes to sleep.
But your warning isn’t due to parasites. It’s from the system voltage dropping too low while running. You have a hidden problem that we haven’t been able to help you find yet. It has to be in the system that manages the alternator or battery at driving speeds. Your battery is appropriate and your alternator tests good. The battery sensor is on the negative battery cable. Maybe there? Or the battery control module (BCM). I’m just throwing out guesses.
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