Observation

The expected answers were:

1.      
     
   1. X – rectifier/diode assembly
   
                                                                           
   2. Function of X in the operation of the alternator
   
   Rectification/conversion of a.c. to d.c.
   
    
   3. Symptoms of a faulty X in the operation of the alternator
   
   
   • Drop in charging output
   • Leakage of a.c. current into the electrical system
   
   

                                                                                                  

   4. How to test the components in X
   
   
   Alt.I
   • Set multimeter to a.c. or d.c. voltage
   
   
   • Turn the dial to diode-test/resistance mode
   
   
   • Connect the test leads to the diode
   
   
   • If a continuous sound is heard in only one direction, diode is in good condition
   
   

   Alt. II

   • Measure voltage drop across diode in forward bias mode
   
   
   • It permits current flow and measures 0.7/0.2 voltage value
   
   
   • It does not permit current flow in the reverse direction and does not measure voltage
   • The diode is in good condition
    
2.   
    
   1. Function of voltage regulator in charging system
   2. To maintain constant output voltage even with varying load. 
   
      
   3. Symptoms of bad voltage regulator

   • Dimming light in headlamps and dashboard elements
   
   
   • Pulsating light  in headlamps and dashboard elements
   
   
   • Dead battery
   
   
   • Unpredictable engine performance
   
   
   • Engine stalling
   
   
   • Engine sputtering
   
   
   • Intermittent acceleration
   
   
   • Over-charging
   
   
   • Under-charging
   
   

              
   It was reported that majority of the candidates that attempted question 4 responded well but for question (a)(iv) which required the candidates to describe how diode (X) can be tested.
   Majority of the candidates, including the high performing ones, did not describe the process of testing diodes appropriately.