Modern excavator repair
Experience and Lessons from Fault Diagnosis of Modern Excavators (18)
5. After replacing the new starter motor, the machine starts normally. 1. During the long-term use of electromagnetic switch components, the contacts will be sintered and bonded due to poor contact, excessive contact resistance, or spark discharge during the closing and breaking of the contacts. Usually pay attention to the service life of such components; personnel with maintenance experience should pay attention to periodically grinding the internal contacts with sandpaper or fine files to enhance the maintenance of the starter motor. 2. The driver of the excavator should be educated: if there is a failure of the motor running after the starter motor is started, the sound of the motor running at high speed can generally be detected. At this time, the power of the starter motor should be immediately disconnected to avoid burning the starter motor. Symptom: The engine start motor cannot start and is accompanied by the sound of a click tower. User requirements: find the cause of the fault and resolve the fault as soon as possible. 1. When starting the motor, use a multimeter to measure the voltage across the battery only 14V. When the motor is not started, the voltage across the battery is 24V. 2. It seems that the problem is when starting the motor.
Due to the large voltage fluctuations at both ends of the battery, the magnetic switch breaks when the motor is started, and it makes a clicking sound. 3． Users are advised to remove the battery from the car and reload it after 12 hours of charging. The problem is resolved. 1. Users report that the car has not been working for a long time. 2. This failure is caused by the machine's non-operation for a long time, and the battery's self-discharge causes a serious shortage of battery power. 3． Tell the user that when the machine is not working for a long time, it is better to remove the negative ground wire. Symptom: The amount of cold air in the air conditioner is too small, and the temperature in the cab is high. User requirements: find the cause of the fault and resolve the fault as soon as possible. 1. Check the compressor working condition, everything is normal. 2. Check the fan motor and its circuit, and found that the speed regulation resistor and controller are normal. 3． Later, when inspecting the air filter inside the air conditioner, it was found that the filter was severely blocked. After cleaning the filter, the fault situation was greatly improved. After replacing the new filter, the fault was completely solved. 4． Ask the driver, since the aircraft was purchased.
The air conditioning filter has never been cleaned, and the installation location of this filter has never been known. 1. To solve the problem, we must adhere to the principle of "easy first and then difficult". 2. When shipping or regularly servicing the machine, don't forget to tell the user where the air conditioning system needs maintenance. Symptom: The engine starts normally when the car is cold, and it is very difficult to start the hot car. User requirements: Requires engine replacement. 1. This is a typical failure caused by early wear of the high-pressure pump, which is usually caused by the dirty fuel used. 2. Remove the diesel filter (single filter) and pour the diesel in the filter into a bowl. It was found that there was a lot of black suspended matter on the diesel and about 1/3 volume of water under the diesel. 3． This is a typical machine failure caused by improper use of oil by the user, and the user is fully responsible. Users understand this. 4． Temporarily cool the high-pressure pump with cold water, and the engine can start immediately. Inform the user that the high-pressure pump must be calibrated immediately. 1. For machine failure caused by improper user oil.
The company should be informed of the machine warranty regulations. 2. When shipping or regularly servicing the machine, repeat the importance of telling users the importance of proper oil use. For machines with a single filter element in the diesel system, the maintenance and replacement cycle of the filter element should be shortened or a crude diesel filter element should be installed. Symptom: The engine stops automatically during engine operation. User opinion: Fix the fault immediately, otherwise replace the engine assembly. 1. According to the user's description, I know that there is no abnormal noise during the operation of the engine. 2. From the general handling experience of such faults, the biggest cause of automatic flameout during engine operation may be caused by a fault in the fuel oil circuit. However, it may also be caused by other reasons such as the fuel cut solenoid valve. 3. Stand on the machine and observe the fuel cut solenoid valve. When starting, it can be normally closed and held. However, the fuel shut-off solenoid valve can't keep working for less than half an hour (the resistance value of the coil inside the fuel shut-off solenoid valve is heated, which causes the pull-in force to decrease).