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Type :
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starter
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Specification :
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24V 3.7KW
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Number of feet :
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9T
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Brand :
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nuojin
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Number :
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QDJ251C/251B 4BD1T，8970298630
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Quality :
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Remanufacture
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Delivery time :
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10 day
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=
The 24V starter of JAC is mostly suitable for JAC’s diesel commercial vehicles and other models. Its installation process aligns with the logic of universal diesel vehicle starter installation, while attention must be paid to the compatibility of the 24V circuit system. The specific installation method and precautions are as follows:
Prepare tools including a socket wrench, torque wrench, and Phillips screwdriver. Confirm that the new 24V starter is compatible with the corresponding JAC model; inspect for no cracks on the housing, no wear on the gear, and complete supporting accessories such as bolts and washers.
Park the vehicle on a flat surface, engage the parking brake firmly, and turn off the engine. Be sure to disconnect the negative battery cable first to avoid short circuits that could damage electrical components during operation. Wear non-slip gloves and safety goggles to prevent hand injuries from oil slippage or eye injuries from part debris.
Locate the starter mounting position at the junction of the engine and transmission. Clean oil stains, rust, and dust from the mounting surface. Simultaneously, inspect surrounding wiring harnesses for aging or damage and repair or replace them if necessary.
Place the new starter stably in the mounting position, ensuring the starter’s mounting holes align precisely with those on the engine side. The starter’s gear end must face the flywheel to prepare for smooth gear engagement later.
Initially install 2–3 long fixing bolts of the starter in place with a wrench, then tighten them to a torque of 37N·m using a torque wrench. Apply moderate force: loose bolts will cause starter vibration during operation, while over-tightening may damage the mounting seat threads.
First, insert the starter’s control wire connector into the corresponding interface and confirm the buckle locks securely to prevent detachment. Next, connect the main power terminal (Terminal 30) and tighten the nut to a torque of 9.8N·m. If a wiring harness bracket is available, install it and tighten its bolts to 8.4N·m, then secure the wiring harness with clips to avoid damage from shaking or friction during vehicle operation. Pay special attention to distinguishing the 24V circuit wires—do not confuse the control wire with the main power wire.
Reconnect the negative battery cable, insert the key, and turn it to the start position. Observe whether the starter gear can engage the flywheel smoothly to start the engine, if the gear retracts promptly after startup, and if there is any abnormal noise during operation.
If weak cranking or failure to start occurs, prioritize checking for loose bolts, poor wiring connections, and verify that the battery voltage meets the 24V standard.
If gear engagement is abnormal, inspect whether the starter mounting position is misaligned, adjust it, and retest.
If the fault persists, there may be a problem with the starter’s internal components, requiring further inspection or replacement.
The core precautions for installing the 24V starter of JAC focus on the characteristics of the 24V circuit and the adaptation requirements of diesel commercial vehicles, covering key dimensions such as safety protection, installation accuracy, and wiring standards. Details are as follows:
Keep the vehicle turned off and the parking brake fully engaged throughout the process. Disconnect the negative battery cable before installation and reconnect it only after completion. 24V circuits have a higher risk of short circuits, so this step avoids burning the starter coil or on-board electrical appliances.
Do not touch the main power terminal and the starter housing simultaneously with metal tools, nor attempt to start the vehicle before wiring is completed. The 24V voltage generates stronger sparks, which may easily cause safety hazards.
Ensure the battery voltage meets the standard (≥24V) to prevent excessive wear of the starter due to low-voltage startup. Meanwhile, avoid reverse connection of the battery’s positive and negative terminals.
The new starter must be clearly marked as compatible with the corresponding JAC diesel commercial vehicle model. Confirm that the voltage (24V), power, and mounting hole spacing match the old unit to avoid installation failure or circuit overload caused by mismatched models.
Before installation, check that the starter gear teeth are free of chipping, the coil is undamaged and non-leaking. Use original or matching-specification accessories (bolts, lock washers) and do not mix non-standard parts to prevent loosening due to vibration.
Verify that the wiring harness specification is suitable for the 24V circuit. Avoid using low-specification harnesses that may cause overheating or short circuits; replace aged or damaged harnesses in advance.
Align the starter’s mounting holes precisely with those on the engine side. Never pry or strike forcefully, as this may damage the mounting seat threads or the starter housing, leading to severe vibration during operation and affecting engagement performance.
Tighten the fixing bolts to 37N·m, the main power terminal nut to 9.8N·m, and the wiring harness bracket bolts to 8.4N·m. Loose fasteners easily cause overheating and poor contact, while over-tightening may result in thread stripping or component deformation.
Face the starter’s gear end directly at the flywheel ring gear. After installation, push the gear gently by hand to confirm smooth telescoping without jamming. Diesel commercial vehicle flywheel ring gears bear large forces, so abnormal engagement gaps can easily cause component damage.
Strictly distinguish between the control wire (thin connector) and the main power wire (thick Terminal 30). 24V circuits are more sensitive to wiring errors—reverse connection or misconnection will directly burn the starter or electrical system. It is recommended to mark the wiring positions when removing the old unit.
Clean oxide layers and oil stains from terminal surfaces before connection to ensure good contact. Secure connectors firmly and fasten the wiring harness to the bracket with clips, avoiding contact with high-temperature engine components or damage from shaking/friction during driving.
If connecting multiple strands of wires, use terminals suitable for 24V circuits and ensure complete insulation to prevent short circuits or leakage.
References：
The precautions regarding the installation method of JAC's 24V starter you previously inquired about are not derived from an exclusive authoritative document on starter installation issued by JAC Motors. Instead, they are a summary of common knowledge integrated from universal specifications in the automotive maintenance field, maintenance guides from professional platforms, and practical industry experience. Specifically, they correspond to the following types of sources:
The universal starter disassembly and assembly guides published on these platforms are one of the core references. For instance, the repeatedly emphasized precautions such as "disconnect the negative battery cable before installation, strictly prohibit tapping tightly fitted components, and recommend performing a 12V no-load test first followed by a 24V no-load test for 24V starters" fully align with the core precautions for installing JAC's 24V starter. Additionally, the specifications for wiring order and component cleaning are consistent with the maintenance common sense on these platforms.
Content from automotive maintenance teaching courseware such as Automotive Electrical Equipment Structure and Maintenance and starter assembly operation instructions released by enterprises is also highly consistent. For example, the courseware emphasizes that after assembling the starter, measurement and adjustment should be conducted before operation testing; the bolt assembly torque standards specified in the operation instructions match the requirements for torque control and post-installation testing during the installation of JAC's 24V starter. These belong to universal technical guidelines in the automotive maintenance field.
Maintenance guides issued by starter-related manufacturing enterprises such as Ningbo Navide Motor include content on checking the firmness of starter wiring, inspecting wear on components like gears and brushes, and avoiding interference in wiring harness arrangement. This content is also an important reference for the precautions for installing JAC's 24V starter. Derived from the universal structure and working principle of starters, such content represents practical industry experience applicable to most 24V starters, including those matched with JAC models.
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