This lesson will instruct the student on how to diagnose (troubleshoot) charging system for causes of undercharge, no-charge, or overcharge conditions. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in an Automotive Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Diagnose (troubleshoot) charging system for causes of undercharge, no-charge, or overcharge conditions.
Given the proper tools and instruction, the student will be able to diagnose (troubleshoot) charging system for causes of undercharge, no-charge, or overcharge conditions, and pass a written test covering the task with 100% accuracy.
One of the jobs of the alternator is to charge the battery as well as power the accessories. If the alternator does not charge the battery properly many circuits will be affected and the automobile may have poor drivability performance.
Remind students that when diagnosing an alternator it is important to first do a load test on the battery for proper charge. If the battery is defective it can have an effect on the alternator performance.
After verifying the battery is good, have students do a visual inspection of the belt, pulley and electrical connections on the alternator. Inform students to check the belt for proper tension. Make sure that all connections are tight and free of corrosion.
Instruct students to hook up tester to alternator and do an output test. Output should be within 10% of manufacturers’ recommendations. With tester hooked up and car started check for voltage regulator output at the battery. Typical voltage will be between 13.5 to 15 volts with the engine at 2000 RPM.
If the voltage is too high, check that the charging system components such as the generator and voltage regulator (if separate) are properly grounded. If the battery voltage is still higher than specified, then there is a likely fault with the electrical connections at the voltage regulator or generator. If the voltage is lower than specifications, there is a fault with the wiring, generator, or regulator (if external). Additional testing is required to help pinpoint the root cause. If the alternator is not supplying the 13.5 to 15 volts it may need to be replaced.
The alternator may also be tested by doing a procedure called full fielding. Full-fielding the alternator determines if the alternator is capable of producing its designed output. This procedure allows the voltage regulator to be bypassed. If the alternator fails this test replacement is probably needed. If it passes it may be possible to replace the voltage regulator only.
Possible Causes for No Charge: 1. Alternator drive belt loose or broken. 2. Voltage regulator fusible link blown. 3. Sticking or worn brushes. 4. Loose or corroded connection. 5. Rectifiers open. 6. Charging circuit open. 7. Open circuit in stator winding. 8. Field circuit open. 9. Defective field relay. 10. Defective voltage regulator. 11. Open diode. 12. Open resistor wire. 13. Slipping drive pulley. 14. Oil soaked brushes. 15. Corroded or loose brush connections. 16. Seized bearings.
Corrections for the Causes of No Charge listed above: 1. Tighten or replace belt. 2. Install new fusible link. 3. Free or replace brushes. 4. Clean and solder connections. 5. Correct cause and replace rectifiers. 6. Correct as needed. 7. Replace stator. 8. Test and correct as required. 9. Replace relay. 10. Replace voltage regulator. 11. Replace diode. 12. Replace resistor wire. 13. Install new key and tighten. 14. Replace brushes. 15. Clean and tighten connections. 16. Replace bearings. Check shaft for damage.
Possible Causes for Undercharging: 1. Loose drive belt. 2. Open stator; grounded or shorted turns in stator windings. 3. High resistance in battery terminals 4. High resistance in charging circuit. 5. Engine ground strap loose or broken. 6. Loose connections. 7. Defective rectifier. 8. Dirty, burned slip rings. 9. Grounded or shorted turns in rotor. 10. Brushes worn. Brush springs weak.
Corrections for causes of Undercharging listed above: 1. Tighten belt. 2. Replace stator. 3. Clean and tighten terminals. 4. Repair cause of high resistance. 5. Tighten or replace strap. 6. Tighten connections. 7. Replace rectifier. 8. Turn slip rings. 9. Replace rotor. 10. Replace brushes and/or springs.
Possible Causes for Overcharging: 1. Faulty voltage regulator ground. 2. Defective voltage regulator. 3. Alternator field winding grounded. 4. Open rectifier. 5. Loose connections.
Corrections for the Overcharging conditions listed above: 1. Ground regulator properly. 2. Replace regulator. 3. Repair grounded field winding. 4. Replace rectifier. 5. Tighten connections.
Objective 1. / Formative assessment / Instructor will observe students as they practice the procedure to assure correct procedure and safety practices are being followed. A checklist will be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.
STUDENT ASSESSMENT: (Assess student progress with performance criteria.)
Objective 1 / Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)