DFFT Electrical Systems 2

Question 1

A vehicle's horn does not work. The fuse is intact. What should be tested next?

Accepted Answer

The horn relay and the horn switch continuity

Answer

After confirming the fuse is good, the relay and switch are the next most common failure points in a simple horn circuit.

Question 2

A vehicle's headlights flicker at idle but are steady at higher RPM. What is the most likely cause?

Accepted Answer

Low alternator output at idle not meeting electrical demand

Answer

Alternators produce less current at idle; if electrical demand exceeds output, voltage drops and lights may flicker until engine speed increases alternator output.

Question 3

During a DFFT electrical test, you find 0.8V voltage drop across a battery-to-starter cable under cranking load. Is this acceptable?

Accepted Answer

No, maximum allowable voltage drop is typically 0.5V for high-current cables

Answer

Excessive voltage drop in the starter cable reduces voltage available at the starter motor, causing slow cranking; maximum acceptable drop is typically 0.5V.

Question 4

A vehicle's battery goes flat overnight despite no obvious loads left on. What is this fault called?

Accepted Answer

Parasitic drain or key-off current draw

Answer

Parasitic drain refers to excessive current draw from a component that remains active after the ignition is off, slowly discharging the battery.

Question 5

What is the correct method to test for a parasitic drain on a vehicle?

Accepted Answer

Connect an ammeter in series between the battery negative terminal and the cable

Answer

An ammeter in series monitors the actual current flowing out of the battery with everything off, allowing the technician to identify which circuit is causing the drain.

DFFT - Driver Fault Finding Test Practice Test

DFFT - Driver Fault Finding Test Practice Test

DFFT Electrical Systems 2