Installation Method of 24V 7.5KW Starter for HOWO A7

I. Pre-installation Preparation

Safety and Power-off

Parts and Tools

• Parts: Confirm that the model of the 24V 7.5KW starter is compatible (e.g., original Sinotruk parts). Check for no cracks on the appearance, clean and corrosion-free wiring terminals, and prepare new gaskets and bolts.

• Tools: Socket wrench, torque wrench, brush, cleaning agent, lubricating grease (e.g., lithium-based grease).

Cleaning of Mounting Surface

II. Installation Steps

Positioning and Pre-fixing

Electrical Connection (in Sequence)

1. Connect the main power terminal (+) of the starter. The nut torque is about 9.8N·m. Ensure the cable is securely fixed and install an insulating protective sleeve.

2. Connect the control plug of the solenoid switch, fasten it in place, and check for no looseness.

3. Install the ground wire with a torque of about 8.4N·m to ensure good grounding.

Lubrication and Gap Adjustment

Re-inspection and Power-on

1. Check the torque of all bolts, firmness of wiring, and ensure there is no interference.

2. Connect the negative battery cable and perform a no-load test: Power on briefly, observe that the drive gear extends and retracts smoothly without abnormal noise; the no-load current and speed shall comply with the 24V starter standards.

3. Start the engine, confirm that the starter engages normally without slipping, and the drive gear disengages immediately after the engine starts.

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Installation Precautions for 24V 7.5KW Starter of HOWO A7

1. Power-off Operation Must Be PrioritizedDisconnect the negative cable of the battery throughout the installation process to prevent accidental start-up of the starter or circuit short circuit. It is forbidden to plug or unplug the control plug or tighten the power terminal when the power is on.
2. Mounting Surface and Parts Must Be Clean and Free of ResiduesClean the oil stains, rust and metal debris on the mounting surface of the engine flywheel housing to avoid insecure fixation or positioning deviation of the starter caused by impurities; check that the flange surface and positioning pins of the starter are free of deformation, and replace the aging sealing gaskets to prevent oil leakage.
3. Bolt Tightening Shall Follow the Principle of “Diagonal Cross + Torque Standard”Tighten the fixing bolts in batches in a diagonal cross sequence, and strictly implement the original factory standard for the final torque (recommended 37N·m). It is forbidden to tighten violently with an extended wrench to prevent thread slipping or starter housing cracking.
4. Electrical Connection Sequence and Terminal Protection

• Wiring sequence: First connect the main power terminal (+) of the starter, then connect the control wire of the solenoid switch, and finally connect the ground wire; the disassembly sequence is reversed.

• Control the torque of the nut of the main power terminal at 9.8N·m, install an anti-loosening gasket, and apply conductive paste on the surface of the terminal to reduce contact resistance; the ground wire shall be connected to the metal surface of the engine body, avoiding connection to the paint layer or rusted parts, with a reference torque of 8.4N·m.

• Fix the wire harness with buckles to avoid contact and friction with high-temperature components and moving components of the engine, so as to prevent insulation layer damage.

5. Strictly Distinguish Between “Permitted Areas” and “Forbidden Areas” in Lubrication Work

• Permitted lubrication areas: Apply a small amount of lithium-based grease to the transmission case bushing, spline shaft and sliding surface of the overrunning clutch. The dosage shall be based on uniform coverage of the surface to avoid excess.

• Absolutely forbidden lubrication areas: Do not lubricate the tooth surface of the overrunning clutch drive gear and the meshing surface of the flywheel ring gear. Grease will cause meshing slip and even burn out the starter in severe cases.

6. Precise Adjustment of Meshing GapAfter installation, adjust the limit nut to ensure that the gap between the drive gear and the limit nut is 1–4mm; after adjustment, lock the lock nut at two positions with a punch to prevent gap change caused by vibration during vehicle operation, which may lead to meshing noise or ring gear damage.
7. Test Procedures Shall Follow the Step-by-step Verification of “No-load → Load”

• No-load test: After connecting the negative battery cable, power on briefly (≤15 seconds each time), observe whether the drive gear extends and retracts smoothly without jamming or abnormal noise; measure the no-load current and speed, which shall comply with the technical parameters of the 24V 7.5KW starter (reference values: no-load current ≤120A, no-load speed ≥3000r/min).

• Load test: Start the engine, confirm that the starter meshes without slipping or continuous abnormal noise, and the drive gear shall retract immediately after the engine starts; the interval between two starts shall be ≥5 seconds. It is forbidden to start continuously for a long time for many times to prevent the starter from overheating and burning out.

8. Protection Under Special Working ConditionsIf the vehicle is used in humid and dusty environments, install waterproof and dustproof protective sleeves on the starter wiring terminals after installation; when used in alpine regions, check the low-temperature starting performance of the starter solenoid switch, and replace the brush assembly suitable for low-temperature environments if necessary.
9. Post-installation Re-inspection Is IndispensableAfter starting the engine and running for 5–10 minutes, turn off the engine and re-inspect: no loose bolts, no heating of terminals, no oil leakage or seepage, and no wire harness interference.

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Core Authoritative Sources

Explanation of Key Clause Sources

1. Power-off and Mounting Surface Cleaning

   Derived from the “Starter Disassembly and Assembly Safety Specifications” in the Sinotruk original factory manual, which requires disconnecting the negative battery cable first and cleaning the mounting surface to prevent positioning deviation and oil leakage.
2. Bolt Torque and Tightening Sequence

   The Sinotruk original factory manual clearly specifies the diagonal crisscross tightening method for fixing bolts with a torque of 37N·m. The torque values of 9.8N·m for the main power terminal and 8.4N·m for the ground wire are referenced from the general specifications for heavy-duty truck electrical connection.
3. Electrical Connection Sequence and Protection

   Complies with the wiring principle of “main circuit first, control circuit second, ground wire last” specified in GB/T 5334-2008. The requirements for terminal conductive paste, anti-loosening gaskets and wire harness fixation are derived from the industry electrical installation specifications.
4. Lubrication Zoning Management

   QC/T 731-2005 stipulates that no oil shall be applied to the drive gear of the overrunning clutch to avoid meshing slip. The lubrication requirements for transmission components are from the Sinotruk original factory maintenance manual.