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2014 ML350 sudden stall, no charging - possible alternator repair
Hi, I'm looking for some insight before replacing parts.My car is a 2014 Mercedes ML350 Base RWD (non start-stop). While driving screen and audio shut off followed by a battery logo with "See owner's manual" message on the dashboard, then a few minutes the car suddenly started jerking and everything on the dash lit up, later the engine stalled. Jump-starting ran it briefly, then it would died again, enough for me to get it on a tow truck. I connected a scanning tool when the car started showing issues and it showed 11.5V with engine on and off, then it dropped to around 10V when it died
What I’ve found so far 3 days (after)
- old AGM battery measured ~4 V, so I replaced it with a new battery. It was only a year old though
- New battery tests healthy: ~12.7 V engine off
- With engine running, voltage dropped to around 12.4 V and continued going down over a few minute test, so the car is clearly not charging
- Scanner showed fault code (ECM - P065B00 The Alternator Has A Malfunction._) plus multiple CAN/ESP errors (doors, moonroof, camera, gps).
- I also noticed black grease around the alternator, especially near a cap/connector area, with baked-on residue on a nearby coolant hose (photos attached below)
- Serpentine belt seams to be good and turning.
At this point it looks like an alternator issue but before I replace it, I’d like to confirm there isn’t something obvious I’m missing. I would appreciate someone assisting me with diagnostics I can do to confirm it's the alternator and possibly find the specific problem. I am also hoping to repair the alternator to save money and gain new experience, unless it's a waste of time on these units.
The short answer is yes, you can rebuild an alternator. They're not a complicated device. The rotating armature produces AC voltage which is then rectified to DC. There's a controller either internal or external that caps the voltage around 14V and tapers it off over time or against battery voltage. The most likely failure is brushes or diodes. When you rebuild it you want to change the brushes, test the diodes and replace the bearings. I expect there's 1000s of YouTubes explaining the process.
Personally I went through that phase and eventually found a shop that actually does the work. Most shops will just pull rebuilt boxes off the shelf and in that case you are subject to whatever source they happen to use. If you can find an old school motor rewinder - the kind with a metal clad bench in the back where little old men sit on stools all day and rebuild starters or alternators - that place is a keeper. Over the last 40 years I've found exactly 2 of those shops in all of western Canada and I'm only certain that 1 of those still exists so don't expect the search to be easy.
(edit) I should have stated that your symptoms are classic alternator failure. You could test the output directly at the alternator but I wouldn't bother.
Last edited by bobofthenorth; Jan 11, 2026 at 10:31 AM.
Thank you. I will pull the alternator out and see what I can find.
I also scanned the ECM with my scanner and got this data: Control Unit Version:
2014 ML350 (M276)
ECM: Bosch MED177
Control Unit: MED177_X
MB No.: 2769011200
Supplier: Bosch
Hardware Status: 11.25.00
Software Status: 11.32.00
Diagnosis Ident: 021E3E
MB Software Object: 0009040300
Live Data – Engine RUNNING
Alternator
Engine Speed: ~758 rpm
Battery Voltage (ECM): ~11.8-12.0 V
Alternator ID: 21
Calculated Alternator Torque: -1.4 Nm
Electrical Fault in Alternator: YES
Mechanical Fault in Alternator: YES
Status of Circuit 61: NO
Camshaft Adaptation Status
Adaptation of Position of Intake Camshafts: YES
Adaptation of Position of Exhaust Camshafts: YES
Position of Exhaust Camshaft Left Bank: -25.0°
Position of Exhaust Camshaft Right Bank: -25.0°
Position of Intake Camshaft Left Bank: +36.21°
Position of Intake Camshaft Right Bank: +36.21°
Live Data - Key ON, Engine OFF
Alternator
Engine Speed: 0 rpm
Battery Voltage (ECM): 12.25 V
Calculated Alternator Torque: -0.91 Nm
Electrical Fault in Alternator: YES
Mechanical Fault in Alternator: YES
Status of Circuit 61: NO
Camshaft Adaptation Status
Adaptation of Position of Intake Camshafts: YES
Adaptation of Position of Exhaust Camshafts: YES
Position of Exhaust Camshaft Left Bank: +0.02°
Position of Exhaust Camshaft Right Bank: -0.13°
Position of Intake Camshaft Left Bank: +0.59°
Position of Intake Camshaft Right Bank: -0.57°
Bad Alternator, just did this on our 2015 ML400 4MATIC, relatively easy to do. But tedious to get out of the engine bay. Might be easier with the ML350 (M276 without the turbos)
Thank you. I will pull the alternator out and see what I can find.
I also scanned the ECM with my scanner and got this data: Control Unit Version:
2014 ML350 (M276)
ECM: Bosch MED177
Control Unit: MED177_X
MB No.: 2769011200
Supplier: Bosch
Hardware Status: 11.25.00
Software Status: 11.32.00
Diagnosis Ident: 021E3E
MB Software Object: 0009040300
Live Data – Engine RUNNING
Alternator
Engine Speed: ~758 rpm
Battery Voltage (ECM): ~11.8-12.0 V
Alternator ID: 21
Calculated Alternator Torque: -1.4 Nm
Electrical Fault in Alternator: YES
Mechanical Fault in Alternator: YES
Status of Circuit 61: NO
Camshaft Adaptation Status
Adaptation of Position of Intake Camshafts: YES
Adaptation of Position of Exhaust Camshafts: YES
Position of Exhaust Camshaft Left Bank: -25.0°
Position of Exhaust Camshaft Right Bank: -25.0°
Position of Intake Camshaft Left Bank: +36.21°
Position of Intake Camshaft Right Bank: +36.21°
Live Data - Key ON, Engine OFF
Alternator
Engine Speed: 0 rpm
Battery Voltage (ECM): 12.25 V
Calculated Alternator Torque: -0.91 Nm
Electrical Fault in Alternator: YES
Mechanical Fault in Alternator: YES
Status of Circuit 61: NO
Camshaft Adaptation Status
Adaptation of Position of Intake Camshafts: YES
Adaptation of Position of Exhaust Camshafts: YES
Position of Exhaust Camshaft Left Bank: +0.02°
Position of Exhaust Camshaft Right Bank: -0.13°
Position of Intake Camshaft Left Bank: +0.59°
Position of Intake Camshaft Right Bank: -0.57°
Perhaps the question is if the alternator overall is bad, or just the voltage regulator. Voltage regulators are a maintenance item on the alternators; however, it still needs a good cleanup.
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