Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Troubleshooting
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Troubleshooting
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Subject: Auto Electrical Works
Class: Senior Secondary 3
Term: 3rd Term
Week: 3
Theme: Auxiliary System
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Tell the signsformalfunctioningunit in the auxiliarysystem. Removewhereappropriate)the faulty link or unit. Service or repair the faulty unit. Replace the repairedor new unit. Test for functionality.
2. 1. Definition of Troubleshooting Troubleshooting in auto electrical works is a systematic process of diagnosing and resolving faults or problems within a vehicle's electrical system. It involves identifying the symptoms, localizing the problem, determining the root cause, and implementing a repair to restore normal functionality. 2.
2. Auxiliary Electrical System The auxiliary system refers to all electrical components and circuits in a vehicle that are not directly part of the engine's primary ignition or fuel management system but are crucial for the vehicle's operation, safety, comfort, and convenience. Examples include the charging system (alternator, battery), starting system (starter motor, solenoid), lighting system (headlights, tail lights, indicators), horn, wipers, power windows, audio system, and various gauges and warning lights. 2.
3. Common Signs of Failure for Various Auxiliary Units (Performance Objective 1) Understanding the symptoms is the first step in troubleshooting.
Battery: Signs of Failure: Engine cranks slowly or not at all (clicking sound), dim headlights when starting, horn sounds weak, dashboard warning lights are faint or do not come on, battery fluid leakage, swollen battery casing.
Nigerian Context: Often due to heat, overcharging, or using non-recommended battery types leading to premature failure, especially in commercial vehicles.
Alternator (Charging System): Signs of Failure: Battery warning light (often a battery icon) illuminates on the dashboard while the engine is running, dimming headlights and interior lights while driving, battery consistently discharges, engine stalling due to lack of power to ignition/fuel system, burning rubber smell (from a slipping drive belt).
Nigerian Context: Common due to heavy electrical load from aftermarket accessories, dust/heat affecting components, or worn belts.
Starter Motor (Starting System): Signs of Failure: Engine does not crank when key is turned (no sound or single click), grinding noise when attempting to start, smoke from the engine compartment during starting, slow cranking even with a good battery.
Nigerian Context: Frequent starting/stopping in urban traffic (e.g., Keke Napep, Danfo) can accelerate wear.
Headlights/Tail Lights/Indicator Lights: Signs of Failure: Lights not turning on, flickering lights, dim lights, only one light working (e.g., one headlight out), indicator flashing too fast or not at all.
Nigerian Context: Blown bulbs, corroded sockets due to humidity, faulty switches, or broken wires from vibrations on poor roads.
Horn: Signs of Failure: Horn does not sound, weak or inconsistent sound, horn sounding continuously without activation.
Nigerian Context: Often due to worn contacts, faulty relay, or poor grounding, used extensively in heavy traffic.
Windshield Wipers: Signs of Failure: Wipers not moving, moving slowly, making scraping noises, only working on one speed setting, not returning to park position.
Nigerian Context: Due to exposure to harsh sun and rain, motor failure, worn linkage, or faulty switch.
Fuses and Relays: Signs of Failure: A whole circuit or multiple components stop working simultaneously (e.g., radio, power windows, and cigarette lighter all fail at once), visible break in the fuse wire, clicking sound from relay but no action from component.
Nigerian Context: Overloading circuits with accessories or short circuits are common causes. 2.
4. Steps in Troubleshooting (Performance Objectives 2, 3, 4, 5) The troubleshooting process generally follows these steps:
1. Symptom Identification (Observe and Verify): Carefully observe and note down all symptoms reported or experienced. Verify the complaint by attempting to replicate the fault.
Ask questions: When did it start? What were you doing? Any recent repairs?
Example: Customer reports "headlights are not working". Teacher should verify by turning on the headlights.
2. Preliminary Checks (Visual Inspection and Basic Tests): Visual Inspection: Look for obvious signs: loose or corroded battery terminals, frayed wires, blown fuses, disconnected connectors, burnt components, unusual smells, fluid leaks.
Basic Tests (without special tools): Wiggle wires, tap components (e.g., starter motor solenoid), check for continuity using a simple test light across a fuse.
Example: Check battery terminals for corrosion, inspect headlight bulb filaments, check the fuse for the headlight circuit.
3. Diagnosis and Fault Isolation (Using Diagnostic Tools): Use of Multimeter: Voltage Test: Measure voltage at various points in the circuit to check for power supply (e.g., battery obvious signs: loose or corroded battery terminals, frayed wires, blown fuses, disconnected connectors, burnt components, unusual smells, fluid leaks.
Basic Tests (without special tools): Wiggle wires, tap components (e.g., starter motor solenoid), check for continuity using a simple test light across a fuse.
Example: Check battery terminals for corrosion, inspect headlight bulb filaments, check the fuse for the headlight circuit.
3. Diagnosis and Fault Isolation (Using Diagnostic Tools): Use of Multimeter: Voltage Test: Measure voltage at various points in the circuit to check for power supply (e.g., battery voltage at the component's input). A low voltage indicates a high resistance or poor connection upstream.
Continuity Test: Check if there is an unbroken path for current to flow (e.g., continuity of a wire, switch, or component winding). An open circuit means no continuity.
Resistance Test: Measure the resistance of components (e.g., motor windings, sensors) to compare with specifications. High resistance can indicate internal damage or poor contact.
Use of Test Light: A simple and effective tool to quickly check for the presence of power (+12V) or ground in a circuit.
Wiring Diagrams: Crucial for understanding the circuit path, identifying components, and locating test points.
Example: If the headlight fuse is good, use a multimeter to check for 12V at the headlight bulb connector. If no voltage, trace back to the switch or relay.
4. Removal of Faulty Link or Unit (Performance Objective 2): Once the faulty component or circuit link is identified, disconnect the battery (negative terminal first) to prevent short circuits. Carefully disconnect wiring connectors, unbolt mounting brackets, and remove the component using appropriate tools (screwdrivers, wrenches).
Safety: Always disconnect the battery before working on electrical components. Use insulated tools.
5. Service or Repair the Faulty Unit (Performance Objective 3): Cleaning: Clean corroded terminals (e.g., battery posts, connector pins) using a wire brush and terminal cleaner.
Resetting Gaps: Adjust contact breaker points in older ignition systems or spark plug gaps (if related to ignition troubleshooting).
Reconnecting Broken Circuits: Solder or crimp broken wires, ensure proper insulation using heat shrink or electrical tape.
Specific component repairs: Replacing brushes in a starter motor or alternator, tightening loose connections within a switch.
Example: Cleaning corroded contacts on a headlight switch or repairing a frayed wire leading to the horn.
6. Replacement of Repaired or New Unit (Performance Objective 4): If the unit is beyond repair (e.g., a shorted motor, badly burnt component, cracked housing), it must be replaced with a new or reconditioned unit. Install the repaired or new unit by reversing the removal process. Ensure all connectors are securely fastened and mounting bolts are tightened to specification.
Example: Installing a new alternator or a repaired starter motor.
7. Test for Functionality (Performance Objective 5): Reconnect the battery (positive terminal first, then negative). Turn on the ignition and activate the circuit or component that was repaired/replaced. Observe if the component operates as expected (e.g., headlights illuminate brightly, horn sounds, engine cranks). Conduct a final system check to ensure no new faults were introduced.
Example: After replacing a fuse for the power windows, test all windows for up/down operation. 2.
5. Safety Precautions: Always disconnect the negative battery terminal before working on any electrical component. Wear appropriate personal protective equipment (PPE) such as safety glasses and gloves. Use insulated tools. Avoid wearing loose clothing or jewellery that could get caught in moving parts or conduct electricity. Be aware of hot components and sharp edges. * Do not short-circuit battery terminals or live wires. 3.
1. Teacher Activities: Introduction (10 min): Begin by presenting a real-life scenario of a vehicle breakdown due to an electrical fault (e.g., a "Danfo" bus failing to start early in the morning). Ask students how they would approach finding the problem.
Concept Explanation (20 min): Define troubleshooting and explain the auxiliary system, using simple diagrams of a car's electrical layout. Discuss common signs of failure for key auxiliary units (battery, alternator, starter, lights, horn, wipers), linking them to Performance Objective
1. Use visual aids like faulty components or pictures. Explain the step-by-step troubleshooting process (identification, preliminary checks, diagnosis, removal, repair/service, replacement, testing).
Tool Demonstration (20 min): Demonstrate the safe and correct use of a multimeter for voltage, continuity, and resistance testing. Demonstrate the use of a test light. Explain how to read basic wiring diagrams (e.g., for a headlight circuit).
Practical Tip:* If actual tools are scarce, use large posters depicting tools and their displays.
Practical Demonstration (30 min): Using a mock-up electrical board or an actual vehicle (if available), demonstrate the process of troubleshooting a specific, common fault (e.g., a non-functional horn or headlight).
Explicitly show: How to identify the fault from symptoms. How to perform preliminary checks (fuse inspection). How to use a test light/multimeter to diagnose power supply/continuity. How to safely remove a component (e.g., a horn unit or relay), addressing Performance Objective
2. How to perform a simple repair (e.g., cleaning contacts, reconnecting a wire), addressing Performance Objective
3. How to replace the unit, addressing Performance Objective
4. How to test for functionality, addressing Performance Objective
5. Emphasize safety precautions at every step.
Facilitation and Supervision: Guide students during group activities and practical sessions, providing support and correcting errors. 3.
2. Student Activities: Brainstorming (10 min): In small groups, students brainstorm common electrical problems they or their family members have encountered with vehicles in Nigeria.
Observation and Note-taking (20 min): Students observe the teacher's demonstration of tool usage and troubleshooting steps, taking detailed notes.
Group Discussion (15 min): Students discuss the importance of each troubleshooting step and the specific tools used. Practical Application (45 min - Group Work): Students, in groups, practice using the multimeter and test light on prepared simple circuits (e.g., a battery, a switch, and a bulb circuit) to check for voltage, continuity, and identify a simulated fault (e.g., a loose wire, an open circuit). If a vehicle or mock-up board is available, groups attempt to: Identify signs of a simulated fault in a specific auxiliary unit. Safely remove a non-critical component (e.g., a fuse, a bulb, a horn unit). Perform a basic "repair" (e.g., cleaning terminals, re-inserting a fuse). Re-install the component. Test for functionality.
Practical Tip:* If actual components are limited, use detailed diagrams or flowcharts for students to follow the process mentally. Students can simulate the actions with hand gestures. align the tabs on the new headlight bulb with the slots in the headlight assembly. Gently push the bulb into place until it is seated firmly.
3. Secure Bulb: Re-attach any retaining clips or springs that hold the bulb in position.
4. Connect Electrical Connector: Reconnect the electrical connector to the back of the bulb. Ensure it clicks securely into place.
5. Reassemble (if necessary): If any covers or dust boots were removed, reinstall them. b.
Testing the headlight for functionality:
1. Turn on Ignition: Switch the vehicle's ignition to the "ON" position (engine does not necessarily need to be running, but it's good practice).
2. Activate Headlights: Turn on the headlight switch to the "low beam" position.
3. Visual Check: Visually confirm that the newly installed right headlight bulb illuminates brightly and consistently.
4. High Beam Check: Switch to "high beam" and verify the high beam filament also illuminates correctly.
5. Compare: Compare the brightness and beam pattern with the left headlight (if working) to ensure consistent operation.
Entrepreneurship and Employment: Troubleshooting skills are directly applicable to becoming a self-employed auto electrician or gaining employment in vehicle repair workshops across Nigeria. With proficiency, individuals can offer mobile repair services for taxis, commercial buses ("Danfo"), or motorcycles ("Okada" and "Keke Napep"), a highly lucrative venture given the constant demand for vehicle maintenance in urban and rural areas. This contributes to local economic activity and creates jobs.
Vehicle Maintenance and Road Safety: Knowledge of troubleshooting allows vehicle owners and drivers to identify and rectify minor electrical faults early, preventing major breakdowns and ensuring critical safety systems (like headlights, brake lights, and indicators) are always functional. This directly enhances road safety for all commuters, a significant concern in Nigeria. For example, a driver noticing dim headlights due to a faulty charging system can prevent nighttime driving hazards.
Cost-Saving and Resourcefulness: In an economy where replacement parts can be expensive or scarce, the ability to diagnose a fault and perform a repair (rather than immediate replacement) is a valuable skill. For example, cleaning corroded battery terminals or repairing a broken wire is much more cost-effective than replacing an entire battery or wiring harness, promoting resourcefulness and sustainability within local communities.