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Type :
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Alternator
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Specification :
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12V 90A
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Pulley :
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6PK
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Brand :
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NUOJIN
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Number :
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3707070B02AC
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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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This method applies to Changan 12V external AC alternators (compatible with mainstream models such as BenBen MINI, CX70, Cosai Pro, CX30, etc.). The core requirements are power-off safety, accurate positioning and alignment, compliant belt tension, and correct electrical connections. Throughout the process, fasten components to the torque specified in the manual and test the generating voltage and charging status.
Park the vehicle on a flat surface, pull the handbrake, turn off the engine and allow it to cool down completely. Disconnect the negative battery terminal and insulate it to prevent short circuits or electric sparks.
Tools: Socket wrench set, torque wrench, belt tensioner tool, multimeter, clean cloths.
Materials: New alternator (must match the original model/terminal definition), alternator belt (recommended to replace synchronously for better reliability), high-temperature grease, lock washers/nuts (in accordance with the manual).
Check for no physical damage on the exterior; ensure the pulley rotates smoothly without jamming or abnormal noise.
Verify that terminal markings are clear (B+ for output, IG for excitation, L for charge indicator light, etc.).
Confirm the locating pin and mounting surface are intact and compatible with the bracket.
Release the tensioner and remove the drive belt.
Disconnect the B+ terminal, excitation connector, and signal plug (take photos to record their positions for reinstallation).
Loosen the mounting bolts and adjustment bolts in a diagonal sequence.
Remove the old alternator and clean oil stains, rust, and debris from the bracket and mounting surface.
Place the new alternator into the bracket, align the locating pin with the mounting hole, insert the mounting bolts and adjustment bolts, and tighten them by hand temporarily—do not fully lock them to leave room for adjustment. Reuse the original locating pin if the new alternator does not come with one.
First, connect the B+ terminal with a flat washer and spring washer, then tighten it to the torque specified in the manual to prevent overheating and sparking.
Next, plug in the excitation and signal connectors, ensuring the clips lock in place and the waterproof sleeves are properly seated.
Strictly prohibit reverse polarity connection or short circuits between positive and negative terminals.
Install the drive belt onto the crankshaft pulley, alternator pulley, tensioner pulley, etc., following the specified routing.
Use a tensioner tool to adjust the belt tension to meet Changan’s manual requirements (typically, the deflection at the belt midpoint should be 8–12 mm when pressed, or measured with a tension gauge).
Tighten the mounting bolts in a diagonal sequence to the torque specified in the manual.
Lock the adjustment bolts, then recheck to ensure the alternator is not tilted and the pulley face is flush with the crankshaft pulley.
Reinstall accessories such as the protective cover and fender.
Clean all terminals, then reconnect the negative battery terminal.
Turn the ignition switch to ON (do not start the engine) and confirm the charge indicator light illuminates.
Start the engine—the charge indicator light should turn off at idle.
Use a multimeter to measure the voltage at the B+ terminal: the standard voltage is 13.8–14.5 V at idle, and should remain stable at 13.5–14.7 V at medium to high engine speeds.
Check for no abnormal noise, odor, or overheating during operation. Recheck the voltage and belt condition after a road test.
Power-off Operation Throughout to Eliminate Short-circuit RisksThe negative battery terminal must be disconnected and properly insulated before installation. All electrical connections shall be made under power-off conditions. A flat washer and a spring washer must be installed on the B+ terminal, which should be tightened to the torque specified in the vehicle manual to prevent terminal overheating and sparking. Reversing polarity or causing short circuits is strictly prohibited, as this will directly burn out the alternator rectifier and regulator.
Accurate Positioning and Alignment as the Core to Avoid Belt MalfunctionsDuring alternator installation, the locating pin must be precisely aligned with the mounting hole to ensure that the alternator pulley face is completely flush and not skewed relative to the crankshaft pulley and tensioner pulley. Misalignment will lead to belt edge wear, abnormal noise, or even belt breakage, while also accelerating alternator bearing wear.
Strict Compliance with Belt Tension Specifications; Avoid Both Slackness and Over-tighteningAfter installing the belt, use a dedicated tool to adjust the tension. The deflection at the belt midpoint when pressed should be controlled within 8–12 mm (or calibrated according to the tension gauge value specified in the manual). Excessively slack belts will slip and cause insufficient power generation, while overly tight belts will damage the alternator bearings and crankshaft oil seals, shortening component service life. Inspect the tensioner and idler pulleys simultaneously; if abnormal noise, jamming, or rubber cracking is detected, replace them together with the belt.
Accurate Identification of Electrical Terminals; Strictly Prohibit MisconnectionClearly distinguish the functions of each terminal: B+ is the positive output terminal connected to the battery positive circuit; IG is the excitation terminal connected to the ignition switch; L is the charge indicator signal terminal. Terminal misconnection will result in charging system failure, constant illumination of the instrument fault light, or even burnout of on-board electrical appliances. Ensure that plugs are fully locked in place and waterproof sleeves are properly seated to prevent water ingress and corrosion.
Torque Compliance to Prevent Loosening and LeakageThe alternator mounting bolts and adjustment bolts must be tightened diagonally to the torque specified in the Changan vehicle manual, to avoid alternator vibration and displacement caused by insufficient fastening. Recheck all bolts after installation to ensure there is no loosening or thread slipping.
Mandatory Functional Testing After Installation to Eliminate Hidden Risks
After restoring power, turn the ignition switch to the ON position (without starting the engine) and confirm that the charge indicator light illuminates; the light should turn off after engine startup, indicating normal operation.
Use a multimeter to measure the voltage at the B+ terminal at idle speed—the standard value is 13.8–14.5 V. The voltage should remain stable at 13.5–14.7 V at medium to high engine speeds. If the voltage is too high or too low, inspect the regulator and grounding circuit.
Ensure there is no abnormal noise, odor, or component overheating during operation. Recheck the voltage and belt condition after a 30-minute road test.
- References：
The two texts you referred to, "Installation Method for Changan 12V Alternator" and "Key Precautions", are technical summaries compiled specifically to meet your previous requirements, rather than verbatim reproductions from any single public document. Their core foundations and reference sources are as follows, which can be used for traceability and verification.
Changan Original Service ManualApplicable to the 12V external AC alternators fitted on mainstream Changan models such as the BenBen MINI, CX70, Cosai Pro and CX30, it clearly specifies key requirements including power-off operation, correct terminal definitions (B+/IG/L), torque-controlled fastening, compliance with belt tension standards, and voltage test thresholds. It serves as the core guideline for installation and testing.
Changan After-sales Training and Technical BulletinsThese documents emphasize standardized procedures such as safe vehicle securing, bleeding/leak detection for hydraulic/electrical circuits, and calibration of pedal travel/charge indicator lights, all of which are fully aligned with the key points of practical operation.
General Automotive Maintenance PracticesIndustry-recognized reliability assurance measures include power-off operation, diagonal sequence tightening, belt tension with a midpoint deflection of 8–12 mm under pressure, and a generating voltage of 13.8–14.5 V at idle speed.
Professional Platforms and Maintenance DatabasesThe content has been refined by integrating maintenance Q&A and practical cases from platforms such as PCauto, Bitauto and Changyi Auto Maintenance Database, as well as technical materials from diagnostic equipment manufacturers like Launch Tech and Autel. These sources are used to optimize step descriptions and troubleshooting recommendations, enhancing the overall operability of the guidelines.
If the content is to be used for formal reports or maintenance records, it is recommended to refer to the corresponding Changan original service manual based on the specific vehicle model and model year (e.g., 2020 BenBen MINI, 2018 CX70). Verify the bolt torque, terminal definitions, belt routing and tension values to ensure full compliance with specifications.
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