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Type :
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AIternator
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Specification :
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14V 120A
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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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738072001 37300-27030
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Quality :
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Remanufacture
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Delivery time :
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10DAY
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This method is applicable to the replacement of the 14V alternator assembly for Isuzu mainstream diesel trucks (non-hybrid variants). The core process is as follows: power-off → alignment and fixation → wiring → belt installation → calibration → power-on test. It is imperative to verify the part number and torque values according to the specific vehicle model, production year, and engine type (e.g., 4JB1, 4HK1, 6HK1) to ensure operational safety and stable power generation.
Tools: socket wrench, ratchet wrench, torque wrench, screwdriver, wire crimping tool, jack with safety stands, safety goggles, work gloves.Consumables: insulating tape, rust remover, thread locker (as required), belt tension gauge (recommended).
Turn off the engine, disconnect the negative battery cable and mark its position clearly. Wait for the capacitors in the electrical system to discharge completely for at least 5 minutes. Clean oil stains in the engine compartment and cover vulnerable pipelines and wire harnesses to prevent damage.
Verify that the part number, rated current, mounting hole positions, and pulley specifications of the new alternator match those of the original unit. Inspect the pulley, voltage regulator, and rectifier bridge for integrity; rotate the pulley to ensure there is no jamming or abnormal noise.
If necessary, remove the right front wheel, wheel arch liner, and lower engine guard, or move components such as the air filter assembly, cooling fan, and expansion tank. Never rely solely on a jack for operation.
Place the alternator on the mounting bracket and align it with the upper/lower and front/rear mounting holes. Install the fixing bolts and nuts (typically upper bolts and lower nuts) but do not fully tighten them—leave a small adjustment margin. Ensure that the axes of the alternator pulley, crankshaft pulley, idler pulley, and tensioner pulley are parallel with no deviation.
First, connect the thick B+ output cable and tighten the terminal nut to a reference torque of approximately 10 N·m, then properly insulate the connection. Next, plug in the field wire/signal wire connector, ensuring it locks securely in place and the pins match the correct configuration.
Inspect for exposed wires and loose contacts. Secure the wire harnesses with clips and keep them away from high-temperature or moving components. For turbocharged models, add extra heat insulation protection.
Route the drive belt into all pulley grooves according to the diagram marked in the engine compartment.
For automatic tensioner models: Use a dedicated tool to release the tensioner, fit the belt in place, then reset the tensioner and confirm that the pointer falls within the standard scale range with no belt twisting or edge detachment.
For manual tensioner models: Pry the alternator (applying force only on the reinforced ribs of the housing) to tension the belt. Press the middle section of the belt—the deflection should be approximately 10–15 mm, or measure the tension to the standard value using a belt tension gauge.
Tighten the alternator fixing bolts and nuts to the torque specified in the repair manual (common values: upper bolts 40–58 N·m, lower nuts 34–54 N·m).
Reinstall all removed components, then reconnect the negative battery cable. Start the engine and observe the alternator operation: no abnormal noise, no belt slipping or squealing.
Use a multimeter to measure the battery voltage: 13.8–14.5 V at idle speed, stable without significant fluctuations when the engine speed reaches around 2000 r/min, and the charging indicator light turns off. Turn on high-power loads such as headlights and air conditioning—the voltage should remain stable within the range of 13.0–14.5 V.
Before installation, disconnect the negative battery cable and wait for the capacitors in the electrical system to discharge completely (at least 5 minutes). This prevents residual electricity from causing short circuits that could burn out the alternator regulator, rectifier bridge, or vehicle Electronic Control Unit (ECU). Reconnect the negative cable only after all mechanical and electrical connections are fully completed; double-check for exposed wires and wiring errors before conducting the startup test.
Never touch the alternator terminals, pulleys, or other components while the engine is running to avoid electric shock or mechanical injury from entanglement with rotating parts. Do not plug or unplug the field wire/signal wire connector when the power is on, as this may generate electric sparks and damage electronic components.
The thick B+ cable of the alternator must be securely connected to the positive battery terminal or designated terminal post. The field wire/signal wire should be connected according to the markings on the connector. Reversing the positive and negative polarities is strictly prohibited. Polarity reversal will directly burn out the internal electronic components of the alternator, which cannot be repaired through routine maintenance.
After completing the wiring, confirm that all terminals are tight and free of exposed wires. Secure the wire harnesses with original equipment manufacturer (OEM) clips to prevent friction against high-temperature engine components (e.g., exhaust pipe, turbocharger housing) or moving parts (e.g., belt, fan), which could damage the insulation layer and cause short circuits. For turbocharged models, install additional heat shields and route the wire harnesses away from high-temperature areas such as the exhaust manifold.
Tighten the alternator fixing bolts and nuts to the torque values specified in the original factory manual (common values: upper bolts 40–58 N·m, lower nuts 34–54 N·m, B+ terminal nut approximately 10 N·m). Under-tightening will cause alternator vibration and belt slipping; over-tightening may strip the threads on the mounting bracket or crack the alternator housing. It is recommended to use a torque wrench for precise operation.For older models, pay attention to potential corrosion of the bracket bolts. Apply rust remover before disassembly to avoid bolt breakage caused by forced twisting.
For automatic tensioner models: Use a dedicated tool to release the tensioner; do not pry violently to prevent tensioner failure. After fitting the belt, confirm that the tensioner pointer falls within the standard scale range with no belt twisting or edge detachment.
For manual tensioner models: Press the middle section of the belt—the deflection should be controlled within 10–15 mm; alternatively, use a belt tension gauge to measure the tension to meet the vehicle-specific standard.
Excessively high tension will accelerate bearing wear and shorten the alternator service life; insufficient tension will lead to belt slipping, reduced power generation efficiency, and even belt squealing.
References：
The two documents you have received, namely Installation Method of 14V Alternator for Isuzu Diesel Trucks and Precautions for Installation of 14V Alternator for Isuzu Diesel Trucks, are original compilations and simplified adaptations based on Isuzu Genuine Repair Manuals, universal specifications for the disassembly and assembly of commercial vehicle electrical components and engine accessories, and common industry testing standards (e.g., idle voltage range of 13.8–14.5V, drive belt mid-span deflection of 10–15mm). They are not directly copied from any single public document or official manual, and are intended for hands-on operation guidance and technical reference for Isuzu mainstream diesel trucks (non-hybrid variants).
Isuzu Genuine Repair Manuals are categorized by vehicle model, production year, and engine type (e.g., 4JB1, 4HK1, 6HK1). These manuals contain precise parameters including bolt torque values, belt specifications, and circuit definitions. In this compilation, universal installation steps and typical parameter values are extracted to facilitate quick and straightforward application.
You may consult the corresponding genuine repair manual for your vehicle’s production year at an authorized Isuzu dealership or after-sales service center. Alternatively, subscribe to or purchase the electronic version via the Isuzu Technical Information System and search for the chapter titled Charging System — Alternator Assembly to cross-check the original content.
Procedures such as disconnecting the negative battery terminal, adjusting drive belt tension, and conducting voltage tests are universal safety and quality requirements for the disassembly and assembly of commercial vehicle electrical components and engine accessories, and are applicable to alternator replacement for the vast majority of diesel trucks.
Parameters such as the idle voltage range of 13.8–14.5V and the drive belt mid-span deflection of 10–15mm are common industry testing and adjustment benchmarks. For precise values, always refer to the repair manual specific to your vehicle’s production year.
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