Auto Electrical Works Paper 2, WASSCE (SC), 2019

Question 2

 

Fig. 1 is the circuit diagram of a system in a motor vehicle.

 

 

image

 

(a)        Identify the:
            (i)         system in Fig. 1;
            (ii)        partslabelled X, Y and Z.

(b)        Table 2 contains some faults associated with the system in Fig. 1.
Table 2

 

Fault

One effect on the operation of the system

One possible remedy

(i)

Low specific gravity of electrolyte

 

 

(ii)

Poor battery earthing

 

 

(iii)

Worn out ring gear

 

 

(iv)

Partial contact of key when closed

 

 

(v)

Worn out pinion gear

 

 

Complete Table 2.

 

Observation

 

(a)        (i)         Starting system          
                                                                                                           
                        (ii)        X – solenoid switch               
                                    Y – flywheel                          
                                    Z – starter motor                                                                                            

              (b)                                                                  Table 2

 

Fault

One effect on the operation of the system

One possible remedy

(i)

Low specific gravity of electrolyte

  • Low battery voltage
  • Damage to battery cell
  • Low cranking ability
  • Recharge battery
  • Replace electrolyte and recharge
  • Change battery

(ii)

Poor battery earthing

  • Slow cranking
  • No cranking
  • Solenoid not actuating
  • Remove, clean and fix cable
  • Replace cable if faulty

 

(iii)

Worn-out ring gear

  • Noisy operation
  • No cranking
  • Damage of pinion
  • Replace ring gear
  • Replace flywheel

(iv)

Partial contact of key when closed

  • Slow cranking
  • No cranking
  • Change ignition switch
  • Clean contact

(v)

Worn-out pinion gear

  • Noisy operation
  • Damage to flywheel ring-gear
  • Change pinion

 

           
The report by the Chief Examiner indicated that majority of the candidates wrongly identified the diagram as charging system instead ofstarting system as required in question 2(a)(i)while the part labelled Y was named by many as ring gear as against the flywheel. The report further stated that a large percentage of the candidates that attempted the question did not respond well to the ‘b’ part.