The Tightness Of The Generator Belt

Feb. 25, 2022

Working principle and function

The car's battery has limited power and must be recharged immediately after discharge, so the car must also be equipped with a charging system. The charging system consists of generator, regulator and charging status indicator device.

The basic principle of the alternator to produce alternating current is electromagnetic induction, that is, through the change of the magnetic flux of the stator winding, the induced electromotive force is generated in the stator winding.


Common generator failures and solutions

The common fault of the generator is the fault of the generator itself, and the fault phenomenon is that the generator does not generate electricity.

Check the tightness of the belt

Visually inspect the belt for breakage or exceeding the wear limit. If it fails to meet the requirements, it shall replace it without delay.

Check the deflection of the belt. When 100N force is applied in the middle of the transmission belt between the two pulley, the deflection of the new transmission belt should be 5 ~ 10 mm, and the deflection of the old transmission belt (that is, installed on the car, with the engine rotation for more than 5 months) is generally 7 ~ 14 mm, specific indicators shall be subject to the provisions of the car model manual. If the deflection of the belt does not meet the requirements, it should be adjusted in time.

Check the tension of the belt. Both the deflection and tension of the belt reflect how the generator is running, so some cars only need to check one or the other. Special tools should be used to check the tension of the belt, and this can be done if conditions permit.

Check wire connections

Check whether the connection part of each wire end is correct and reliable.

Generator output terminal B must be secured with spring washer.

For generators connected through connectors, the connection between the socket and the harness plug must be locked and not loose.


Check the noise

Generator failure (especially mechanical failure), such as bearing damage, shaft bending, etc. , abnormal noise will be emitted when the generator is running. In the inspection process, gradually increase the engine throttle opening, so that the engine speed gradually increase, while monitoring the generator is abnormal noise. If there is abnormal noise, disassemble the motor and disassemble it for maintenance.

Generator voltage test

If the car is equipped with a catalytic exhaust purifier, the engine should not run for more than 5 minutes when doing this experiment.

When the engine is stopped and the electrical equipment on the vehicle is not in use, the battery voltage is measured, known as the reference voltage or reference voltage.

Start engine, keep engine speed at 2000 RPM, measure battery voltage without using on-board electrical equipment. This voltage is called no-load charge voltage. The no-load charging voltage should be higher than the reference voltage, but not more than 2V. If the voltage is below the reference voltage, it means the generator is not generating and the generator, regulator and charging system wiring should be thoroughly checked.

When the engine speed is still 2000r/min, turn on electrical accessories such as heaters, air conditioners, and headlights. When the voltage is stable, the battery voltage is measured, called the load voltage. The load voltage shall be at least 0.5V higher than the reference voltage.


If there is a problem, check the charging line voltage drop when the charging current is 20A. Connect the positive electrode of the voltmeter to the armature (B+) terminal of the generator, and connect the negative electrode of the voltmeter to the pile head of the positive electrode of the battery. Voltmeter reading should not exceed 0.7V; Connect the positive pole of the voltmeter to the regulator housing and the other end to the generator housing. The reading of the voltmeter shall not exceed 0.05 VOLTS. When one end of the voltmeter is connected to the generator housing and the other end to the negative battery, the voltage indication shall not exceed 0.05 VOLTS. If the indicated values are inconsistent, clean and tighten the appropriate connectors and mounting brackets.

 Weichai Genset

B Terminal current test

Shut off the engine, remove the battery grounding cable terminal, remove the original lead wire from the armature (B+) terminal of the silicon rectifier generator, and connect 0 ~ 40A ammeter in series between the removed lead connector and the armature terminal. The positive terminal of the voltmeter is connected to the armature terminal, and the negative terminal is connected to the body.


Cut off all the electrical switches on the car.

Reinstall the battery ground cable connector and start the engine so that the generator operates at slightly above rated load. At this time the ammeter reading should be less than 10A, voltage indication value should be within the regulator regulation value range.

Turn on the main electrical equipment of the car (such as headlights, high beams, heaters, air conditioners, wipers, etc.). , so that the current number is greater than 30A, and the voltage number should be greater than the battery voltage.

When the engine is turned off, remove the battery ground cable terminal first, then remove the voltmeter and ammeter, and reinstall the "armature" line of the cycle motor and the battery ground terminal.


If the voltage value exceeds the specified voltage upper limit, it is generally the voltage regulator fault; If the voltage value is far below the lower voltage limit and the current is too small, check the generator's single diode or single armature windings for faults.


Guangxi Dingbo Power Equipment Manufacturing Co., Ltd. established in 2006, is an manufacturer of diesel generator in China, which integrates design, supply, commissioning and maintenance of diesel generator set. Product covers Cummins, Perkins, Volvo, Yuchai, Shangchai, Deutz, Ricardo, MTU, Weichai etc. with power range 20kw-3000kw, and become their OEM factory and technology center.

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