310S Electrical and Electronic Systems 4

Question 1

A technician notices the battery warning light flickers at idle but goes off at higher RPM. What should be checked first?

Accepted Answer

The drive belt tension and alternator output at idle

Answer

Flickering at idle suggests the alternator is not producing sufficient output at low RPM, which could be caused by a slipping or worn drive belt, or an alternator with a failing stator winding or diode.

Question 2

What is the purpose of the diode trio in an alternator?

Accepted Answer

To supply DC current to the rotor field coil from the stator output

Answer

The diode trio taps a small portion of AC output from the stator, rectifies it to DC, and feeds it to the rotor field coil. This makes the alternator self-exciting after initial field current from the battery.

Question 3

What is the correct procedure for testing a fuse without removing it from the fuse box?

Accepted Answer

Use a test light or voltmeter to check for power on both sides of the fuse with the circuit energized

Answer

Testing both exposed test points on top of a blade fuse with a test light or voltmeter while the circuit is on confirms power is passing through. If only one side has power, the fuse is blown.

Question 4

What causes alternator whine in the audio system?

Accepted Answer

AC ripple from a failing rectifier diode coupling into the audio signal wiring

Answer

A failing diode in the rectifier bridge allows AC ripple to pass into the DC electrical system. This AC noise couples into audio signal wiring, producing a whine that increases in pitch with engine RPM.

Question 5

A vehicle equipped with daytime running lights (DRLs) has one DRL that does not illuminate. The headlights work normally. What is the most likely cause?

Accepted Answer

A burned-out DRL bulb or LED unit

Answer

Since the headlights work normally, the bulb wiring and ground are functional. The most likely cause is a burned-out DRL-specific bulb or LED unit, as many vehicles use separate elements for DRL and headlight functions.

Red Seal Auto Tech 310S Practice Test

Red Seal Auto Tech 310S Practice Test

310S Electrical and Electronic Systems 4