Electronic instruments are relatively precise and have high technical requirements for maintenance. Maintenance, should comply with the relevant provisions of various automobile maintenance manual. If necessary, electronic instruments and equipment should be sent to a professional maintenance unit for repair.
The electronic instrument display board and motherboard are not only easy to damage, but also expensive, use and overhaul with care. Unless otherwise specified, the full voltage of the battery must not be applied to any of the input terminals of the instrument panel. High impedance instruments should be used when checking voltage and resistance. Improper use of automotive gauges can often cause serious damage to microcomputer circuits, so special attention should be paid to this during gauge maintenance.
For electronic instrument panels that need to be serviced, first cut off the power supply, and then disassemble the electronic instrument panel in the order of disassembly. Special care should be taken not to knock or vibrate during disassembly to avoid damaging the electronic components.
Disassembly of the electronic instrument panel should be carried out in accordance with the order of disassembly, do not use excessive force when disassembling, in order to prevent its own good components due to excessive force and damage. When disconnecting connectors or terminals before removing the instrument panel assembly, the battery terminals should be disconnected first. Replacement of electronic instrument components, should be careful not to let the body and the replacement components of the integrated circuit lead terminal contact, spare parts should be placed in the nickel-plated bag, do not remove from the bag in advance, do not touch the various parts of the connector when removed, to prevent the body from static electricity caused by the damage to the components.
When repairing the electronic instrument panel, whether working in the car or on the bench, the workplace or maintenance personnel should not be charged. Therefore, static protection devices should be used in the operation, usually a wrist strap connected to the body and a conductive pad to place the electronic components.
The battery must not be disconnected while the engine is running, as this can cause a transient reverse electromotive force, leading to damage to the instrument.
When handling the electronic speedometer/odometer circuit board, the original plastic case must be used to avoid damage caused by electrostatic induction. If you accidentally touch the connector of the circuit board, the readings of the instrument will be eliminated, and must be sent to a professional repair before use.2. The common inspection methods of electronic instrumentation Many of the electronic instrument panels of automobiles are controlled by microcomputers with self-testing functions. As long as the instruction is given, the electronic controller of the electronic instrument panel will systematically check its main display device. If there is a malfunction, the driver will be warned of the malfunction of the display system in different ways, and a fault code for the malfunctioning part will be stored so that it can be called up and pointed out during repairs. When it is confirmed that the instrument panel is faulty, it should be tested.
1) self-diagnostic test with the automotive fault diagnostic instrument on the self-diagnostic instrument will make the following actions: the tachometer first full scale after reaching 3000rpm, the thermometer first full scale after reaching 90 ℃, the gasoline gauge first full scale after reaching 1/2, the odometer first full scale after reaching 100km, the full-screen display, all indicators/warning lights are on, the buzzer sounds. 2) Use the rapid detector Perform the test. The quick tester can send out analog signals from various sensors and can quickly detect the location of the fault. If the instrument panel can work normally when a signal is input to it with the tester, it means that there is a problem with the sensor or its circuit. If the display still fails to show, connect the tester directly to the relevant input socket on the dashboard. At this point, if the display can be displayed normally, the wiring harness and connectors are faulty, otherwise, the surface instrument panel is faulty.
3) Use the computer quick tester, which can simulate the signals from the fuel flow and speed sensors, or you can input the tester's signals from different parts, thus checking that the sensors and wiring harnesses of the computer and the display unit are working properly.
4) Check with LCD tester. During the test, the tester can provide reference input signals for the instrument panel and message center directly on the instrument panel, and can check the working status of the message center. The purpose of this test is to further verify if there are any malfunctions on the instrument panel.
Detection of Common Faults in Electronic Instrument Clusters
Faults in automotive electronic instrument display systems are usually found in sensors, connectors, wires, individual gauges and displays.
When inspecting and repairing, the sensor circuits should be disconnected or removed and checked one by one with test equipment.
Check the sensor. First, disconnect the sensor circuit or remove the sensor and check each one with an instrument. For a variety of resistance sensor inspection, usually using the method of measuring its resistance value to determine its good or bad, that is, the measured resistance value and the standard resistance value to compare to determine whether the sensor is faulty. If the measured value is less than the specified value, it indicates that the sensor is short-circuited internally, otherwise the sensor has poor contact. Sensors are usually non-removable and non-repairable components. If there is any failure, it can only be replaced with a new one. Check the connectors. Cars that use electronic instruments usually require many connectors to connect the wiring harness to the instrument panel. These connectors are usually marked with different colors to identify which part of the connection it belongs to. To ensure a reliable and secure connection, the connectors are equipped with a locking mechanism. When inspecting them, you can either look or feel them by hand. The connector unit should be complete and intact, and the plugs and sockets should make reliable contact and be free of corrosion. When touching the connector by hand during the operation of the instrument, there should be no obvious temperature sensation. If the temperature is too high, it means that the connector contact is poor, and the cause should be found and eliminated.
Individual instrument troubleshooting. If an individual instrument on an electronic instrument fails, check all parts associated with that instrument. First, check the connection of each wire, including the contacts of each connector, and whether the wiring is damaged, grounded, shorted, or open. , then test the instrument and sensor separately with testing equipment to find the cause of the problem, repair it, and replace the components with new ones if necessary.
Display troubleshooting. Once the electronic instrument panel display device, line failure, should be adjusted to the instrument panel display device static display state, carefully observe whether there are other faults, on the faults at this time, the use of testing equipment and its related circuits or devices for careful inspection. If only one or two line segments do not light or do not show, it shows that the logic circuit board through the multiplex transmission of the pulse signal is correct, may be part of the display device is not working properly, encountered in this case should be further inspected, belonging to the poor contact should be fastened to ensure that the circuit is smooth; if the electronic device itself has a problem, should be replaced by the display device or circuit board. @2019