ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsMedium
A vehicle's high-beam headlights are inoperative, but the low-beam headlights function correctly. The high-beam indicator light on the dashboard also does not illuminate when activated. What is the MOST likely cause?
- ABurned out high-beam filaments in both headlight bulbs
- BA short circuit in the turn signal system
- CAn open circuit in the low-beam wiring
- DA faulty headlight switch
Show answer & explanationAnswer & explanation
Correct answer: D. A faulty headlight switch
If both high beams are inoperative and the high-beam indicator light also fails to illuminate, it strongly suggests a lack of power or signal from the high-beam control, which is typically handled by the headlight switch or multi-function switch. If only the filaments were burned out, the indicator light would still illuminate.
Why the other options are wrong
- A. If only the high-beam filaments were burned out, the high-beam indicator light on the dashboard would still illuminate when the high beams are selected, as the switch and circuit up to the bulbs would still be functional.
- B. A short circuit in the turn signal system would likely cause turn signal malfunctions or a blown fuse, but not specifically affect the high beams or their indicator light.
- C. An open circuit in the low-beam wiring would affect the low beams, which are stated to be functioning correctly, and would not explain the high-beam issue.
High-Beam Inoperative Diagnosis
When both high beams and the high-beam indicator light are inoperative, the fault typically lies in the control circuit (e.g., headlight switch) rather than the bulbs themselves.
- Indicator light status is crucial.
- Both high beams affected.
- Points to a common control point.
Memory trick: High Beam Out, Indicator Too? Switch is the Clue!