Auto Electrical Works Paper 2, WASSCE (SC), 2018

Question 6

 

  • Fig. 5 is a schematic diagram of the fuel gauge of a motor vehicle.


    (a)        Identify the parts labelled X, Y and Z.
    (b)        Name the part of the vehicle where Z is located.
    (c)        State the function of the following in the operation of the fuel gauge in Fig. 5:
    (i)         bimetallic arm;
    (ii)        voltage regulator;
    (iii)       heating coil.
    (d)       Give one reason why the pointer is at E.
    (e)        State the effect of pouring more fuel into the tank on parts labelled X, Y and Z.

Observation

   The candidates were expected to copy and complete the table.

(a)  

X – float                                                         
Y – resistor/rheostat/variable resistor            
Z – gauge unit/indicator                                                                                 

 

(b) Dashboard/panel board/instrument cluster                                                                

 

(c)

(i) Bimetallic arm – deflects the pointer.                                                          

(ii) Voltage regulator – stabilizes alternator output voltage/maintains
constant voltage supply to the heating coil/gauge unit/indicator.                 

(iii)       Heating coil – increases the temperature of the bimetallic strip                   

 

(d)       Reason why the pointer is at E

  • The fuel left in the tank is in reserve.
  • It is below what the indicator/gauge can display
  • The variable resistor is at maximum/highest position

 

(e)        Effect of more fuel in the tank on X, Y and Z
X – to rise                                                       
Y – to reduce/decrease                                   
Z – to rise/deflect towards F

  

Question 6 required candidates to understand the principle of operation of the fuel gauge. It was reported that only a few candidates showed a good understanding of the principle of operation of the fuel gauge.          Their performance was reported to be generally poor. More practical and hands-on experience were recommended.