Deck 21: Lighting and Signaling Circuits

Question 1

Technician A says that the bulb trade number is the same for all bulbs of the same size. Technician B says that a dual-filament bulb has different candlepower ratings for each filament. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Answer 1

The bulb trade number for each type of bulbs is different. It defines the size, shape, the number of filaments, and the amount of light produced. The dual-filament bulb has different candle power ratings for each filament so that the power of the bulb can be adjusted as per the requirement.
Hence, technician A is wrong and technician B is correct.
Thus, the correct option is
.

Question 2

Why should the exact same trade number of bulb be used as a replacement?

Answer 2

Trade number is used on bulbs and is defined as per ANSI.
Trade number determines the size, shape, number of filaments and candle power which is the amount of light produced.
While replacing a bulb it should be kept in mind that the trade number of both the bulbs should be same because the bulbs with same trade number have same voltage and wattage. If bulbs with different trade numbers are used, then it may cause damage to the bulb and circuit.
Therefore, exact same trade number bulb should be used as replacement to avoid any damage to the component.

Question 3

Two technicians are discussing flasher units. Technician A says that only a DOT-approved flasher unit should be used for turn signals. Technician B says that a parallel (variableload) flasher will function for turn signal usage, although it will not warn the driver if a bulb burns out. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Answer 3

The DOT flasher turn signals are designed to transmit the current to light in front and rear. This type of flasher units requires current to flow through both the bulbs. If anyone bulb is not working then the turn signal will give a steady light so that the driver can come to know that turn signals are not working.
The parallel flasher will function for turn usage and it also warns the driver as the load is completely transferred to one bulb which starts blinking rapidly, but it will not provide and warning to the driver if a bulb burns out.
Hence, both the technicians are correct.
Thus, the correct option is
.

Question 4

Why is it important to avoid touching a halogen bulb with your fingers?

Question 5

Interior overhead lights (dome lights) are operated by doorjamb switches that ________.

A) Complete the power side of the circuit
B) Complete the ground side of the circuit
C) Move the bulb(s) into contact with the power and ground
D) Either a or b depending on application

Question 6

How do you diagnose a turn signal operating problem?

Question 7

Electrical feedback is usually a result of _______.

A) Too high a voltage in a circuit
B) Too much current (in amperes) in a circuit
C) Lack of a proper ground
D) Both a and b

Question 8

How do you aim headlights on a vehicle equipped with aerodynamic-style headlights?

Question 9

According to Chart 21-1 , which bulb is brightest?

A) 194
B) 168
C) 194NA
D) 1157

Question 10

If a 1157 bulb were to be installed in a left front parking light socket instead of a 2057 bulb, what would be the most likely result?

A) The left turn signal would flash faster.
B) The left turn signal would flash slower.
C) The left parking light would be slightly brighter.
D) The left parking light would be slightly dimmer.

Question 11

A technician replaced a 1157NA with a 1157A bulb. Which is the most likely result?

A) The bulb is brighter because the 1157A candlepower is higher.
B) The amber color of the bulb is a different shade.
C) The bulb is dimmer because the 1157A candlepower is lower.
D) Both b and c

Question 12

A customer complained that every time he turned on his vehicle's lights, the left-side turn signal indicator light on the dash remained on. The most likely cause is a _______.

A) Poor ground to the parking light (or taillight) bulb on the left side
B) Poor ground to the parking light (or taillight) bulb on the right side, causing current to flow to the left-side lights
C) Defective (open) parking light (or taillight) bulb on the left side
D) Both a and c

Question 13

A defective taillight or front park light bulb could cause the ________.

A) Turn signal indicator on the dash to light when the lights are turned on
B) Dash lights to come on when the brake lights are on
C) Lights-on warning chime to sound if the brake pedal is depressed
D) All of the above

Question 14

A defective brake switch could prevent proper operation of the __________.

A) Cruise control
B) ABS brakes
C) Shift interlock
D) All of the above