Modern excavator repair
Experience and Lessons from Fault Diagnosis of Modern Excavators (17)
Replace it. But two or three days later, the same failure occurred again. 2. According to the photos taken by the service personnel, it is found that the alarm switch has been seriously deformed. See that its installation position is close to the turbocharger. It is judged that the alarm switch is damaged because it is too close to the turbocharger. Due to its high temperature, the casing Deformation can cause damage. 3. After changing the installation position of the alarm switch to keep it away from the turbocharger, the failure has not occurred. 1. For the occurrence of a fault, it is necessary to judge the cause of the failure, and not to change what is bad, without judgment. If this is the case, often the same fault will occur again. 2. The same applies to the application for parts on the report. The agent is required to write the cause of the failure. In this way, the agent's ability to deal with the failure can be improved on the one hand, and the shortcomings in the installation or design of our products can be found in time. It can also increase the success rate. Symptom: The starting motor does not rotate. User requirements: find the cause of the fault and resolve the fault.
1. Smell the starter motor with your nose. 2. In the power-off state, use a multimeter to detect a group of normally open contacts of the start relay, and the measured resistance is not infinite. 3． After analysis and judgment, it can be known that the internal contacts of the start relay sintered, causing the starter motor power circuit to not be cut off, and running the motor for a long time caused the motor to overheat and burn out. 4． After replacing the new start relay and start motor, the machine starts normally. 1. During long-term use of relays, 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 sanding the internal contacts of the relay with sandpaper or a fine file. 2. The driver of the excavator should be educated: if there is a fault that the motor is still running after the starter motor is started, the sound of the motor running at high speed can generally be detected, and the power of the starter motor should be immediately disconnected.
Avoid burning the starter motor. Symptom: When starting the engine, the starting motor does not turn. User requirements: Replace the starter motor. 1. Use a multimeter to check that the voltage across the battery is about 25V. 2. When starting the motor, check that the voltage at the motor input is about 10V. 3． Turn off the main power switch and touch the battery pile heads with your hands. It is found that two pile heads have high temperatures. 4． Remove the battery cable, and use sandpaper to polish the battery connection cable and the battery pile head. Restart the machine and troubleshoot. 1. This failure is caused by the contact resistance between the battery pile head and the battery connection cable being too large, and the voltage drop from the battery to the motor is too large when the motor is started (the instantaneous current is extremely large). 2. Educate users to regularly take care of their machines, especially the battery connection must be in good contact. Symptom: The engine cannot be started. User requirements: find the cause of the fault and resolve the fault. 1. Open the battery box cover and find a wrench lying on the battery.
2. The inspection found that the battery pile head and the wrench had been severely ablated. 3． During the conversation with the driver, I learned that the machine had just been subjected to 2500 hours of regular maintenance by the driver himself. 4． After analysis and judgment, it can be known that the driver will put the maintenance wrench on the battery after use up, and the wrench slides during the machine operation, which causes the battery to short circuit. 1. When doing machine maintenance or repair work, do not place other conductive items such as wrenches on the battery to prevent short circuits. Symptom: The starting motor does not turn and the machine cannot be started. User requirements: find the cause of the fault and resolve the fault. 1. Smell the starter motor with your nose. 2. Check the startup circuit and find that everything is normal. 3． Removed the starter motor from the engine and disassembled the motor. It was found that the contact disk and contacts of the starter motor electromagnetic switch were sintered. 4． After analysis and judgment, it can be known that the sintering of the contact disk and contacts of the electromagnetic switch causes the starter motor power circuit to not be cut off, and the motor is overheated and burned due to long-term operation of the motor.