Session 9: Maintenance and Servicing of Major Electrical Accessories
Module 5: Auto Electrical System
Textual Question-Answers
Check Your Progress
Fill in the blanks
1. During the troubleshooting of a horn assembly, if the fuse is blown,
it should be ………….. and the horn should be tested again.
Ans: replaced
2. Electric fuel pumps can be of two types: the flexible diaphragmtype and the motor-driven …………… type.
Ans: rotary
3. To adjust the parking position of windshield wipers, the limitswitch cover should be turned in the direction ……………… to themotor crank rotation.
Ans: opposite
4. If the oil pressure indicator lamp continues to glow even when oil
pressure is adequate, the most likely cause is a ……………….. pressuresensor.
Ans: faulty
5. The purpose of cleaning the top of the fuel tank before removingthe fuel pump is to ensure a clean …………. for the pump.
Ans: mounting surface
6. In an electronic return-less fuel system, the Fuel Pump Control
Module (FPCM) controls the voltage supplied to the fuel pump to achievethe desired fuel …………… requested by the Engine Control Module(ECM).
Ans: pressure
Multiple Choice Questions
1. What is the purpose of testing switches and relays in a vehicle’s electrical system?
a) To adjust the sound quality of the horn
b) To determine the horn frequency
c) To check for voltage at the power feed terminal
d) To diagnose their serviceability
Ans: d) To diagnose their serviceability
2. What should you do if a horn in a single-horn system does notsound when the horn button is pressed?
a) Replace the horn relay
b) Clean and tighten the horn switch ground connection
c) Check the circuit fuse
d) Replace the horn switch
Ans: c) Check the circuit fuse
3. What is the advantage of an electric fuel pump over a mechanical
pump in a vehicle’s fuel system?
a) It depends on the engine drive
b) It requires less maintenance
c) It is affected by under-bonnet temperatures
d) It can be located away from the engine
Ans: d) It can be located away from the engine
4. What is a key factor that can cause fuel pump failure?
a) Low fuel level in the tank
b) Excessive fuel pressure
c) Use of high-octane fuel
d) Frequent use of additives
Ans: a) Low fuel level in the tank
Answer the following questions
1. Discuss the importance of maintenance and servicing of majorelectrical accessories in a vehicle.
Ans: Maintenance and servicing of major electrical accessories areimportant to ensure reliable operation, safety, and comfort of the vehicle.
Proper maintenance helps prevent sudden failures of components such as horn,
wipers, fuel pump, gauges, and warning systems. Regular inspection, cleaning,
and testing improve the service life of accessories, reduce repair costs, andensure accurate functioning of vehicle monitoring systems.
2. Draw the circuit diagram of following.
a. Dual Horn assembly
Ans: The dual horn circuit consists of battery, fuse, horn relay, horn switch, two horn units connected in parallel, and ground.
b. Electrical fuel pump
Ans: The electrical fuel pump circuit includes battery, ignition switch,
fuse, relay, fuel pump motor, and ground connection.
c. Electrical fuel gauges (balancing coil type and thermostatic type)Ans: The balancing coil type fuel gauge circuit includes battery, ignitionswitch, fuel gauge unit with two coils, sender unit, and earth.
The thermostatic type fuel gauge circuit includes battery, ignition switch,
heating coil, bimetal strip, sender unit, and ground.
d. Oil pressure gauge (balancing coil type)
Ans: The oil pressure gauge circuit consists of battery, ignition switch,
balancing coil gauge, pressure sender unit, and ground.
e. Temperature gauge
Ans: The temperature gauge circuit includes battery, ignition switch,
temperature gauge, temperature sender unit, and earth.
f. Electric Speedometer
Ans: The electric speedometer circuit includes vehicle speed sensor,
control unit, speedometer gauge, power supply, and ground.
g. Two-speed windscreen wipers
Ans: The two-speed wiper circuit includes battery, fuse, wiper switch,
resistor, wiper motor, park switch, and ground.
3. Explain the different faults, causes and remedies of the followingautomobile accessories.
a. Dual Horn assembly
Ans: Faults include horn not sounding or weak sound. Causes are blownfuse, faulty relay, poor grounding, or defective horn. Remedies includereplacing fuse, cleaning connections, or replacing horn unit.
b. Electrical fuel pump
Ans: Faults include no fuel delivery or noisy pump. Causes are cloggedfilter, low fuel level, or worn motor. Remedies include cleaning or replacingfilter, maintaining fuel level, or replacing pump.
c. Electrical fuel gauges (balancing coil type and thermostatic type)Ans: Faults include incorrect fuel level indication. Causes are faulty senderunit, open circuit, or poor grounding. Remedies include checking wiring,
replacing sender or gauge unit.
d. Oil pressure gauge (balancing coil type)
Ans: Faults include incorrect readings or warning lamp glowing. Causesare faulty sender or wiring fault. Remedies include replacing pressure senderor repairing wiring.
e. Temperature gauge
Ans: Faults include overheating indication or no reading. Causes are defective temperature sender or open circuit. Remedies include replacingsender and checking connections.
f. Electric Speedometer
Ans: Faults include no speed indication or erratic reading. Causes arefaulty speed sensor or wiring. Remedies include replacing sensor or repairingwiring.
g. Two-speed windscreen wiper
Ans: Faults include wiper not working or incorrect speed. Causes are faultyswitch, resistor, or motor. Remedies include replacing switch, resistor, ormotor.
Activity
1. Make a list of major electrical accessories of a vehicle.
Ans:
1. Electrical accessory: Horn
2. Electrical accessory: Windshield wiper
3. Electrical accessory: Fuel pump
4. Electrical accessory: Instrument cluster gauges
2. Prepare a poster showing a circuit diagram of an electrical
speedometer, oil pressure warning light, and electrical fuel gauge(balanced coil type and thermostatic type) of a vehicle.
Ans The poster should clearly show labeled circuit diagrams of an electric speedometer, oil pressure warning lamp circuit, fuel gauge of balancing coil
type, and fuel gauge of thermostatic type with power supply, sender units, and ground connections.
Try yourself
