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Type :
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Alternator
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Specification :
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12 volts, 150 amperes
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Pulley :
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5PK
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Brand :
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NUOJIN
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Number :
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A6401540502
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Quality :
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Remanufacture
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Delivery time :
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30 days
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The installation of a Mercedes-Benz 12V 150A alternator shall follow the process of power-off → positioning → disassembly → cleaning → installation → wiring → belt installation → matching → verification. The key points lie in compliance with torque specifications, correct electrical connections, proper belt tension, and ECU/BMS matching to ensure stable charging and system compatibility. ⚙️
Verify the VIN, engine model (e.g., M112/M113/M272, etc.), and alternator OE number (e.g., A0009061102, A2721540002, 0124525054). Confirm that the alternator meets the 12V/150A specification, and that its rotation direction and number of belt grooves match the requirements.
Socket/wrench set (8mm, 13mm, 17mm are commonly used), torque wrench (5–50Nm), belt tensioner tool, crowbar/rubber hammer.
Multimeter/voltmeter, OBD diagnostic tool (compatible with Mercedes-Benz ECU/BMS), terminal cleaning brush, insulating tape, high-temperature grease.
Protective gear: gloves, safety goggles, fire blanket, insulated tools.
Turn off the engine, engage the handbrake, and shift to P/N gear.
Disconnect the negative battery terminal and insulate it.
Operate on a cold engine and keep away from high-temperature engine components.
Remove the drive beltUse a belt tensioner tool to press down the tension pulley, remove the belt and mark its routing direction. Replace the belt if it is aged or cracked.
Disconnect electrical connectionsRemove the B+ terminal protective cover, loosen the 13mm nut to take off the main cable. Disconnect the excitation wire (D+/F, 8mm) and the plug, and make clear marks to prevent reverse connection.
Loosen the fixing boltsRemove the upper and lower fixing bolts (17mm is common) and the positioning bushing. Gently move the alternator to disengage the wiring harness and take out the old unit.
Clean the installation positionRemove oil stains, rust, and carbon deposits from the bracket, bolt holes, and contact surfaces. Replace damaged bushings/gaskets if necessary.
Positioning and pre-fixingPlace the new alternator into the bracket, align the bolt holes, insert the bolts and pre-tighten them (do not fully tighten), ensuring the bushing is in place.
Tighten the fixing boltsTighten the bolts according to the vehicle-specific torque (e.g., approximately 42Nm for M112/M113 engines, 35–45Nm for M272 engines). Avoid over-tightening to prevent bracket damage or under-tightening which may cause vibration.
Electrical connection
B+ main cable: Tighten the 13mm nut to a torque of approximately 10–12Nm and reinstall the protective cover.
Excitation wire (D+/F): Tighten the 8mm nut to a torque of approximately 5Nm. Ensure the plug is fully inserted and locked.
Ensure the cables have no interference, do not contact high-temperature components, and are securely fixed.
Install the drive beltInstall the belt according to the original routing direction, use the tensioner tool to reset the tension pulley. Check that the belt has no deviation or distortion.
Belt tension calibration
Automatic tensioner: Confirm that the pointer is within the green zone.
Manual tensioner: Apply a 10kg force at the midpoint of the belt; the deflection should be 8–12mm (slightly larger for double-groove belts).
Start the engine and let it idle for 2 minutes, then turn off the engine and recheck the tension and routing direction.
Connect the OBD diagnostic toolAccess the "Engine Control Module (ECM)" or "Electrical System" menu.
Perform alternator initializationSelect "Alternator Settings", "Charging System Matching" or "Component Replacement Learning", and input the new alternator parameters (12V/150A).
BMS calibrationAccess the "Battery Management System" menu and perform "Battery Registration" or "Charging State Reset" to ensure the ECU correctly identifies the new alternator.
Clear fault codesClear historical fault codes after matching to avoid false alarms.
Power-on checkReconnect the negative battery terminal, turn the key to the ON position, and check that the charging indicator light illuminates (normal condition).
Start-up testMeasure the battery terminal voltage at idle speed with a multimeter; it should be 13.5–14.5V. The voltage should remain stable without significant fluctuation when loads (headlights, air conditioning) are turned on.
Dynamic testRaise the engine speed to 2000rpm; the voltage should remain between 13.8–14.7V with no abnormal noise or belt slippage.
OBD recheckRead the ECU/BMS data stream to confirm that the alternator output current and voltage regulator status are normal, with no new fault codes.
Electrical safetyThe negative battery terminal must be disconnected before disassembly and installation to prevent short circuits. The B+ cable and excitation wire must not be reversely connected.
Installation clearanceThe distance between the alternator and surrounding components shall be ≥10mm. Keep away from the engine exhaust port; install a heat shield if necessary.
Cable specificationThe cross-sectional area of the B+ main cable shall be ≥70mm² (for 150A) to ensure current-carrying capacity and avoid overheating.
Necessity of matchingMercedes-Benz new models (after 2005) must be matched via OBD; otherwise, charging abnormalities or system alarms may occur.
Subsequent inspectionRecheck the belt tension and bolt torque within 1000km of driving to ensure long-term stability.
References：
The "Installation Method for Mercedes-Benz 12V 150A Alternator" provided is not derived from a single official or authoritative source, but rather a practical technical summary integrated from multiple types of materials. The following is an explanation of its information sources and composition:
The core basis: Torque parameters, bolt specifications, ECU/BMS matching paths (e.g., "Alternator Settings", "Charging System Matching"), and OE number examples (A0009061102, A2721540002) are all consistent with the alternator disassembly and installation chapter in Mercedes-Benz's official Workshop Information System (WIS).
Process framework: The steps of "power-off → belt removal → electrical disconnection → bolt loosening → cleaning → installation → wiring → belt installation → matching → verification" refer to general alternator installation tutorials on platforms such as PCauto and Autohome, emphasizing safe operation and standardized processes.
Supplementary details: Belt tension calibration (automatic tensioner pointer in the green zone, manual deflection of 8–12mm), multimeter testing methods, and fault troubleshooting (e.g., constant illumination or non-illumination of the charging light, abnormal voltage) are integrated from experience content on automobile maintenance forums (e.g., Qiche Dashi) and practical operation guides.
This text is an integrated technical summary without specific source labeling (e.g., a specific manual page number or website link). However, its content complies with Mercedes-Benz vehicle maintenance specifications and industry standards, and can be used as a reference for practical operations.
Query the Original Factory ManualEnter the vehicle VIN or chassis number (e.g., W211), obtain the alternator disassembly and installation chapter for the corresponding model through the Mercedes-Benz WIS system or authorized maintenance stations, and verify the torque, bolt specifications, and matching steps.
Verify OE NumbersThe OE numbers in the text (e.g., A0009061102, A2721540002) can be queried through the Mercedes-Benz Electronic Parts Catalog (EPC) to confirm their applicability to the target model.
Refer to Authoritative PlatformsGeneral processes can be verified through alternator installation tutorials on platforms such as Autohome and PCauto; practical details of ECU matching can be supplemented through maintenance platforms such as Qiche Dashi.
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