Auto Electrical Works Paper 3, WASSCE (SC), 2022

Question 2

  1. Fig. 3 is the diagram of the instrument panel on the dash board of a motor vehicle.  
  2.           (i)  Identify the units labeled P, Q, R and S.
    (ii)  State the symptom of fault that can be indicated by symbols T, U, V, W and X.

    1. If M and N blink simultaneously and continually, what does this indicate?

     

     

    1. Table 2 contains some symptoms of fault in the auxiliary system of a motor vehicle. Complete it by stating two possible causes of each of the symptoms given.

    Table 2


    S/N

    Symptom of fault

    Possible causes

    (i)

    Horn honks continually after a single push

     

     

    (ii)

    Wiper blade does not oscillate when switched ON

     

     

    1.       Fig. 4 is the diagram of a starting system.
  3.             (i)  State:
    I. the type of starting system in Fig. 4;
    II. one reason for your answer in 2 (c) (i)I;
    III. one other type of starting system apart from the one illustrated in Fig.4.

     

     

     

            (ii) Table 3 contains some components of the system in Fig. 4. Complete it by stating one
    function and symptom of fault of each of the components illustrated in Fig.4.
    Table 3


    Component

    Function in system

    Symptom of fault

    Battery

     

     

    Solenoid

     

     

    Starter motor

     

     

The expected responses were:

  •   (i)       The units labeled P, Q,R and S in Fig. 3

P – Fuel level/guage indicator
Q – Speedometer
R – Tachometer
S – Water temperature guage/indicator
                                                                                         
(ii)   The symptom of fault that can be indicated by symbols T, U, V, W and X
T – low oil pressure
U – check engine
V – battery/charging system problem
W – tyre pressure problem
X – fog light is on

 (iii)   The M and N blink simultaneously and continually indicates

  • Hazard/take caution/emergency
  •                                                         Table 2

S/N

Symptom of fault

Possible causes

(i)

Horn honks continually after a single push

  • Faulty relay
  • Partial contact
  • Faulty switch
  • Short circuit

(ii)

Wiper blade does not oscillate when switched ON

  • Faulty switch
  • Blown fuse
  • Disconnected linkage
  • Faulty wiper motor

                                                                                                            

  •  (i) I.    The type of starting system in Figure 4     

   – inertia starter system
II.   The reason for your answer in 2(c)(i)I

  • Solenoid is not fixed/mounted on the starter motor

                                                                                                               
III. Mention another type of starting system apart from the in Figure 4

  • Pre-engaged starter system

                                                                                                           
(ii)                                    
Table 3

 

S/N

 

Component

 

Function in system

 

Symptom  of fault

I

 

Battery

  • Feeds/supply voltage to the solenoid

 

  • No clicking sound in solenoid

 

II

 

Solenoid

  • Twitching of current from the battery motor

 

  • No clicking sound in solenoid
  • No output seen when terminal are tested

III

 

Starter motor

  • Converts the electrical energy from the battery to mechanical energy to drive the fly wheel

 

  • Noisy operation
  • No cranking
  • Low cranking speed

 

                                                                       

Questions 2 required candidates to show an understanding of the starting system and show familiarity with the different component parts and functions. The Chief Examiner reported that majority of the candidates showed only little knowledge of the starting system of a motor vehicle.