Tài liệu học tập cơ bản khái quát về động cơ và các bộ phận trên ô tô phiên bản tiếng anh. Tài liệu này nhằm giúp chúng ta tiếp cận được cấu tạo chức năng của các bộ phận của xe. Với tài liệu này giúp các bạn sinh viên ngành cơ khí ô tô tiếp cận được những kiến thức cơ bản về ô tô và đồng thời nâng cao kiến thức tiếng anh. Bộ tài liệu này được soạn thảo bởi trường đào tạo và huấn luyện nghề ở Canada.
Chapter 16 General Electrical System Diagnostics and Service Electrical Problems • Opens – Are breaks in the circuit that stop current flow • Shorts – Are unwanted paths for current • High Resistance – Occurs when there is unwanted resistance in a circuit Shorted Circuit • A circuit with an unwanted path for current to flow • Can cause uncontrolled high current flow • Caused by damaged insulation, loose wires and connections, and improper wiring Short to Ground High-Resistance Circuits • • • • Unwanted resistance in a circuit Higher resistance decreases current flow Corrosion at connectors common The corrosion becomes an additional load and creates a voltage drop • The added resistance in figure B reduces the voltage available for the light Electrical Wiring Diagrams • Also called schematics • Does not show location or actual appearance of components • Symbols are used to represent components • Diagram may illustrate one system or one part of a complex system Electrical Testing Tools • Circuit Testers (test lights) – Are used to identify opens or shorts – Can be non-powered or powered • Multimeter – Measures the voltage available at any point in the circuit – Also measures resistance and current Wiring • Check insulation – Broken, frayed, or damaged insulation can cause short circuits • Inspect ground connections • Perform a voltage drop test on the wire Troubleshooting Logic • • • • Remember three types of circuit problems Perform voltage checks Take measurements at a connector Use adaptors to front and back probe connectors Using Wiring Diagrams • One of the most important resources • Shows relationships of circuits • They illustrate: – – – – Wires by number or color coding Wire cross-section size Ground connections Wire connection points Testing for Opens • If possible, start testing at the load component • Check for voltage on the power side of the component – If voltage is present, check the ground side – If voltage is not present, test all connections working toward the battery – If voltage is present at a connection, the open is between it and the previously tested point Testing for Opens (Cont’d) • If the power side of the circuit tests good, test the ground side – Use a jumper wire to bypass the ground side of the circuit, and if the component works, check all ground side connections • If both the power and ground circuits test good, the load component is open Testing for Shorts • Use an ohmmeter to check resistance of the circuit • If there is a short, the resistance will be less than specified • If the short is between two circuits, components may operate when not intended Testing for Unwanted Resistance • Typically caused by corrosion, loose or poor connections, frayed or damaged wires • Check voltage drop across the load • Check sections of the circuit to find the unwanted resistance Common Causes of Wiring Problems • • • • Corroded terminals Loose terminals Frayed, broken, or oil-soaked wires Faulty insulation Wire Repair Considerations • • • • • • Type of repair required Ease of access to the damaged area Type of conductor Size of wire Circuit requirements Manufacturer’s recommendations Replacing a Terminal • Identify the type of terminal and locking clips • Remove the terminal • Install and solder new terminal • Reinstall the terminal into the connector ... of time and voltage • Time and voltage displays can be adjusted Graphing Multimeters (GMM) • Displays voltage, resistance, current, and frequency as a waveform • May included a signal and data... Connect the DMM and move wiring and note when the beeping stops DMM Safety Guidelines • • • • • • • Use only as designed to be used Never use a damaged meter Ensure battery is secured and enclosed... components • Symbols are used to represent components • Diagram may illustrate one system or one part of a complex system Electrical Testing Tools • Circuit Testers (test lights) – Are used to identify